i had the same issue as some other people here, where they couldn't get iTunes to come up, and it kept bringing up the license agreement. I'm not quite sure what fixed this issue, but here's a list of things I've done (not in any particular order, because I've done some of these multiple times)...
1. unstalled iTunes, Quicktime, and iPod updater
2. removed all references to iTunes and Quicktime in my registry
3. reinstalled iPod updater from my cd
4. reinstalled standalone Quicktime (from a link somewhere in this discussion board)
5. reinstalled iTunes from my cd
6. reinstalled iTunes 6.0.2 (because I was still crashing when updating my iPod)
7. updated my iPod via the updater
8. rebooted my computer multiple times
9. turned off NIS and followed Lorraine's tips
10. cussed at this problem (didn't fix anything but it's better than putting my fist through the monitor!)
Any other input will be very appreciated. All I know is, I updated both iTunes and the iPod updater, and when I update my iPod, it goes through the end (looking at the x of x countdown in the bar at the top of the screen), then I get the Windows "iTunes is experiencing problems and will now close" message.