If you use a disk imaging system, for example, Ghost, you can back up your whole Operating system and programs on a second drive, or DVD's When you reload your operating system fresh, activate your programs that you want to keep activated.
Then backup the C: drive on another Drive or DVD's.
Then, if the C: Drive messes up, you can overwrite it with your disk image from your second drive, or DVD's
Also, some programs are registered to your Drive Volume serial Number. If you look it up, and on reload, use a program that allows you to change the serial number, the program will activate. But not in all cases.
Just Sone thoughts. I think it's stupid to only allow so many installs on an owner's machine.(it should be locked to a computer's Hardware to prevent pirating) Who wants to buy the program again?