said by wascallywabbit :
This is not your hardware; there is a definite problem with the iTunes 5.0 installer (particularly when upgrading). See this thread for suggestions on the apple forum:
[Apple.com]Home > iTunes > iTunes for Windows > Installation & Upgrades > Bonjour won't allow iTunes Install.
The Wabbit
I went to Apple's site and found a useful article in the Support section that was about the exact Error 1920 I was getting. It said to either activate some service with instructions on what to do or disable Norton Internet Security 2005 while installing. Well, since I have NIS 2005, I disabled it while installing, and voila! iTunes and QuickTime installed perfectly. I see QuickTime .movs now have a new icon as seen in folders and such...But there isn't really anything much different that I can find, except for the User Interface, which is a
little bit more friendly. I'm just glad that this terrible mess is finally cleared up and I can continue to use my computer as normal.
Apple better
fix this problem quick, or they will have many more unhappy users of their software and potential customers of the same.