I save installs in a folder right now but they are never run again even after years so I don't see the point especially because newer versions make them obsolete. There may be only a couple that need this.
It was a different story in the past where I'd have to reload the OS after 6-12 months. Now it's stable beyond years. Even the image I haven't had to reuse.
I've had instances where an "upgrade" to a program was inferior, for me anyway, and I went back to a version I'd downloaded previously. I have a downloads folder on my NAS where I keep all that stuff and from which I can install on all my Windows machines. There's tons of stuff there I'll never use but HD space is so cheap now, it hardly matters.
I'm running Windows 10 64bit on this laptop but figure go back to Windows 7 64bit sometime soon. I'll back up the current install first, but my hope is that going back to Win7 will stop an extremely annoying anomaly (I consider it that) in that a swipe across trackpad doesn't move the cursor but instead causes all my open apps to tile. I have to hit ESC or click the app I was using to get back to business. I've tried a number of things to stop it, I figure it's a Win10 feature, I just can't turn it off. People running Lenovo T61's at
http://forum.thinkpads.com mostly say stay away from Windows 10, and they say it with obvious disdain and animosity for Microsoft. I seem OK with it (32bit) on one of my T60 laptops but on the T61, I'm going to have to either restore a Win7 image or install fresh. Well, I'll try it. I never had the problem when I was running Win7 64bit on this machine. It happens sometimes, not all the time, but very frequently. I just don't understand it.