Any time I add something major, and by "major" I mean software that cost me a lot of money, I do an image of the hard drive on to another hard drive.

And this is where I get on my "experience" soapbox and say NEVER NEVER NEVER buy through download only. ALWAYS get media. I bought a piece of hardware from a company called Dacal like 8 years ago that stores 150 CDs with a software interface where all my CDs and DVDs are. Everything I have ever purchased is in that library, down to drivers for NIC cards. When I need something, I load "CDLIB", find it, click it, and the box spits out the CD that holds what I need.

Also, as was mentioned, backup backup backup. I wrote a small batch file I called back2thumb.bat that is little more than

copy C:\documents\*.* h:\documents /Y
copy C:\songs\*.* h:\songs /Y

and so forth, where h: is an 8 gig thumb drive. That copies everything in those directories to my backup drive and overwrites existing files automatically. If you prefer to not automatically overwrite and be prompted every time, make the switch /-Y and it will ask if you want to overwrite. I use the switch because I know I want to, but that is your call. Just make sure you label your thumb drive if you have more than one that looks the same.. LOL!!