Technically, you could just let WinXP format it as one large NTFS partition. There are many who think it's a waste of time trying to "partition" your data separate from your OS and apps or anything like that. Others swear by it.
Anything that manages to destroy your OS partition is probably going to destroy the drive so much that you can't access your data anyway, unless you just do something really stupid like delete the C partition, or have a virus/worm that deletes files or formats the C drive.
If you have actual data that you'd be upset to lose, you should have some sort of backup, even if it's just CDR. I use a firewire connected external hard drive. USB2.0 would also be good for the task, but USB1.1 is far too slow unless you just don't care about how long it takes to make a backup.
My particular setup is to have two 20GB partitions. The C drive has WindowsXP and all my applications and games. Anytime I download something that I want to keep for awhile, but don't necessarily need to have backups of, I put it on the D drive. I also put temporary files there when I rip a CD to MP3, and any ISO's of CD's that I happen to have but don't need to keep permanently. This just makes these files easier to navigate to, without having to keep them on my Desktop or create a shortcut to whatever folder they're in. I don't do anything like putting savegame files onto the D drive for "protection" or anything like that, because the D drive is just as likely to get hosed as the C drive is.
The advantage here is that I don't run a backup on anything that I don't need to have backed up which saves time. I keep my MP3's (all of which except for 1 particular song I do have legal CD's of
🙂) on the firewire backup drive, so they don't run a risk of getting lost with the main drive, and I don't have to make repeated backups of the rather large amount of data they represent.
If you do something like segregating your apps and your OS on different partitions, then you have to backup all the partitions, and either backup stuff you don't need, or manually de-select items for backing up. My way just saves me a little bit of time, and may not be what you prefer. If your data files are so important that you see a need to put them on a separate partition for "safety", then you should be putting them on separate media as a backup anyway.
However saving your data files to another partition DOES make some sense in some cases, since you don't have to go retrieve them and move them to a backup if you find a need to reformat the C drive and reinstall the OS; if you already have always saved them to another partition, then you don't have to worry about losing them when you format. However that doesn't apply with applications these days, as so many make modifications to the Registry and require settings in it to run properly. You'd need to reinstall them anyway, so there's no point to putting them on another partition.
When you install WinXP, if you're not going to use a single partition, you should tell it to make the one partition whatever size you want for the C drive, then install XP. Later after you've gotten Windows set up, you can go into the Disk Management utility and format the other partition or partitions. This just saves a little time, since you can continue to use the system to download any updates or whatever you may need (though you'd need to avoid too much disk activity, since that'd slow down the format).
Here's one guide.
There's not really much to "explain" about partitioning. It's quite simple if you have any technical inclinations and just sit down and walk through it, but would probably be hella hard for my mom to understand. It can get complicated if you start doing things like using multiple OSes, but with just WinXP, it's pretty simple.
For once,
there's also an AT FAQ that could be good reading. I don't necessarily agree with it though. Some of the assumptions are, in my opinion, flawed, or look at the topic from a very simplistic angle. But it may help you to make your own decisions.
