I had to re-build my machine and I had the original software CD's but I couldn't find the Product keys, which were on the original CD sleeves. I know there are ways to look in Windows Registry, but that can get complicated for novices.
I found the Magical Jelly Bean Keyfinder software very easy to use and install, it's the super-easy way to find lost product keys and lost serial numbers for operating systems like Windows XP and Windows Vista and for many other programs and games.
You'll need the original product key or serial number that came with your program before you can reinstall the software!
I hope this helps anyone who finds themselves in the same situation.
Edit: It may register a false positive on some antivirus suites