I need a bit more information... what do you mean that "data just seems to go missing every time" ?
Like, a folder you think you have is suddenly gone? Or a movie/media fila/installed game you think you have is missing or no longer functional?
Or are we talking data corruption to the point where Windows will no longer boot, or something along those lines.
Data doesn't just "go missing" - you've either got a source of corruption in hardware, a source of corruption in software (malware), or a source of corruption or user error between the keyboard and the chair (you). It's basically gotta be one of those three, or a derivative of one of those three.
Now then, on the subject of shrinking your PC- that's an admirable goal in my opinion.
The main differences, in my mind, between ITX and MicroATX is that ITX has a single PCI-Express slot and 2 DIMMs, where mATX can have more than one PCI-E slot (my current mATX board has 3) and can still have 4 DIMMs on mATX. Also, more vendors tend to integrate WiFi on ITX systems, but that's really just a function of what motherboard you choose.
When looking at cases, ITX cases are generally divided into two categories - for gaming, or for NAS/server work. Make sure you pick up the gaming one, otherwise you won't have room for a dual-slot GPU. The server ones can have a ton of hard drive slots - sometimes way more than even a normal tower case - the DS380 I'm looking at you. Also, lots of ITX cases will run with the SFX form factor for their PSU, rather than ATX.
mATX cases aren't typically so different than their full ATX counterparts, and I'd offer that the market for dedicated mATX cases (as in, those that cannot also accept full ATX) is relatively small.
Well, it's kind of hard to explain in full. This might get lengthy, but we'll go drive-by-drive:
Kingston SSD: One day, it just wouldn't boot. Started up with a flashing cursor, like it had no OS. As a solution, I grabbed my (then-fresh) WD Blue drive and threw the OS on it. After that, I plugged in the SSD as a mass storage drive. I could see everything there, including the OS files. Given the SSD was known to have some controller issues, I figured it was the beginning of the end, and decided I'd get a new SSD for my birthday.
Samsung SSD: This replaced the Kingston. After maybe 4-5 months, see above. The PC acted like the OS didn't exist. I sent the drive back to Samsung for repair, just in case. It came back with a firmware update and no reported problems. In the meantime, I decided to format the Kingston, install the OS on it, and give it a try short-term. It worked just fine, and still does (though I've since reinstalled W10 on the Samsung and have it running fine as well). Two SSDs, same problem that seems to show no issue with either drive.
WD Blue HDD: This is where the fun started, and continues to exist, and it's a story with holes (simply because I wasn't there when things went awry). After setting up the Kingston (While the Samsung was out for repair), I hooked the WD back up as a storage device. However, as a lazy American, I didn't bother with a format (didn't have the space for a proper backup). This meant I left Windows on there, not that it affected anything when it wasn't the boot drive. However, I got home a week or so back, and it was a mess. The PC had restarted, IDK when. Somehow, the Kingston got lost by the BIOS, and decided to boot to the Blue drive. This encountered some problem, as there was some fatal, "explorer.exe" error greeting me when I got home (I think 12/23 night). Restarted the PC, got the Kingston back up as the boot drive. Now, the Blue's just showing as "NTFS" in the File Explorer, with 0 bytes used and 0 bytes available. If I try to use it, I just get "E:\ is not accessible. Access is denied." Searching comes up with the theory of a partition screwup. I used WD's Data Lifeguard, running multiple tests. No bad sectors, all tests passed perfectly (also tried SeaTools at another AT user's suggestion). After trying about 4 different partition repair/recover programs. I finally got one that worked. I found the 600-ish GB of media files I was trying to save on the Blue HDD. In that program, I got 4 partitions. Two were very small, seemingly recovery/system things from Windows. The third was about 2 TB in size (the Blue's a 3TB drive), which seemed to be where the OS was installed. Lastly, there's a fourth partition. It's called "Unallocated space." While the first 3 are NTFS, there's no file system attached to this thing. Sure enough, this is where I found my missing data. I have since extracted that stuff, and am reinstalling Data Lifeguard to wipe that drive and see if it can be saved.
WD Black HDD: I've had this drive since the original build in 2009 (got the Kingston around 2014, the WD Blue at Christmas in 2015, and the Samsung in May 2016). I got the Blue simply because I was getting to, and over, the 640 GB Black's limits. I used it to throw my video files on from the Blue recovery (music went to the Samsung SSD, as the video files were taking too much space). I also grabbed my important files (mostly school projects) from the Kingston SSD and put them in a backup folder on this drive. So, the Black's got a "restore videos" folder with the files from the Blue, and a "restore documents" from the Kingston. I watched
Red Dwarf off the recovery from the Blue just fine Friday night. Last night, I go to do it again. It says the link is broken. I ran a repair on the Black, and it put the "restore videos" folder back, no problem. Then, it dumped the "restore documents" one, and I can't find it again (I imagine I could fish it out with the partition recovery program, but the files are still on the Kingston, so fuck reliving that headache I spent 5 days trying to rectify).
That pretty much covers it--two SSDs randomly unable to boot. A HDD with an unmarked partition with 750 GB of data I spent almost a week unable to access on a drive I can't even format without low-level access tools. Folders and partitions disappearing at random. Pinpointing the cause is really hard because it's happened on multiple drives with new and old Windows installs, and it's not been in the same, consistent way. It sounds like malware to me, but IDK where from, and I've had too many varied problems to figure out what the cause would be. That's why I've said I intend to nuke all 4 drives, start fresh, back up data, and see what happens. Some of the stuff can't just be tossed (school/work projects, music I can't get anywhere any longer), so hopefully the source isn't malware hidden in those files. I'm going to also keep the bulk of my video files, we'll see what happens. If it all fails again, MAYBE I try just dumping all data and starting fresh, but I'm not of the belief this is a malware matter rooted in data files acquired years ago.
Regarding the recommendations:
So mini-ITX means no carrying over an ATX PSU? That kind of sucks, but isn't unexpected at all. I'm totally unsure how I want to approach it. My plan has been to go with a small PC as a secondary device in a few months, after Zen's out. It was to be just a small box with the Haswell chip at the core, with no video card. It would JUST play video and music files, nothing else, so getting a video card would be senseless. If I wanted to play games, that's what the new build (likely with Zen and Vega) is for!
If I blame the board, it leaves me two routes: get a new board for my current PC, or accelerate the shrink of the Haswell system. The former means spending probably $75 on a board I'll toss aside in a few months. The latter means spending probably $125 on a video card that I will likely never need again in a few months (though it would be an upgrade on my current one, since it's a 2009 HD 5850). It also means that the short-term problem gets a long-term fix sooner, but forced me into buying a case, board, and PSU early.
The slot restrictions shouldn't matter. I only use 2 8GB RAM sticks, and I don't do a dual-GPU setup. However, the question I run into is, which video cards and PSUs am I to look at? The 5850 was known as a pretty long card, so I can't imagine I could fit it into a mini-ITX case (plus, note that the 5850 has MASSIVELY GREATER idle and load power draws than even an RX 480, so it needs to go, haha). That then leaves me wondering which cards I can fit into it. Maybe PC Part Picker can answer a lot of this for me with its compatibility filter?
Note that many of those, are "slim" cases, with a (sometimes proprietary) PSU integrated, which require low-profile video cards. Not an ideal solution, except perhaps for a HTPC that also requires a full-size optical and 3.5" HDD.
Also, if the build is for HTPC, rather than gaming, consider a purpose-built mini-PC, like a Brix or NUC or similar. (I'm using an ASRock DeskMini right now. It's one of the few mini-PCs that takes desktop CPUs.) Note that the purpose-built mini-PCs don't accommodate a dGPU, unless you get one with a TB3 port, and an external GPU chassis (pricey!).
That really isn't a good solution. I'm not going into the market of buying 2 PCs. This is about repurposing a set of hardware I already own--particularly the CPU, RAM, SSD, and HDD I have in my current build (I have 2 SSDs and 2 HDDs, so one of each would go to the smaller build). That, and I can get the OS free through my school, so we're talking about a build that just required a case and board, unless I need a new PSU. The GPU would be a lower-end, optional thing to carry me to the new build, so I can keep playing
Rocket League and start playing
Civ V again (though they might be passably doable on the HD 4600 GPU). I'd sooner get a device to cast my PC to my TV for media consumption than buy a second TV, I'd just like to not have my current PC just get tossed when it has some perfectly fine stuff inside.