I need help launching iTunes...

I have had iTunes 7.3 for months, and have used it on OS Windows 2000 Professional with SP 4. After I installed some educational software a couple of weeks ago, I could no longer open i
Tunes. I received the error, “iTunes has encountered errors and will be closed by Windows. I have tried all of the solutions suggested by Apple and none of them works. Any thoughts?
I wonder if my settings have been changed. But I do not know how to change them. Or, is there an alternative to iTunes that will run on my OS? I would like to have the songs I have already bought on iTunes.