The last iTunes version that is compatible with Windows 2000 is 7.3
You need to download the windows 2000 version
http://www.apple.com/support/downloads/itunes732forwindows2000.html
Then uninstall all the iTunes related programs listed in this article which is actually for XP:
http://support.apple.com/kb/HT1925
Then install the 2000 compatible iTunes.
If you get a message about a later version library when you try to start iTunes, you have to recreate the library from the xml file:
http://support.apple.com/kb/HT1451
I am afraid if you want iTunes 8 you will have to ugrade your operating system or get a new PC.