Recurring problem

When I plug my iPhone 3G into my comfuser's USB port & open iTunes, all is fine except for my preferences.

In iTunes (10.5.1.42) I clicked Edit>Preferences>Advanced & changed the iTunes Media Folder Location from C:\Users\C\Music\iTunes to P:\Music, ticked 'Keep iTunes Media folder organized', unticked 'Warn me if iTunes is not the default player for audio files' then exited iTunes & disconnected the iPhone from the comfuser. I then deleted the C:\Users\C\Music\iTunes folder.

But everytime I open iTunes, the iTunes Media Folder Location is set back to C:\Users\C\Music\iTunes & the folder is recreated, 'Keep iTunes Media folder organized' is unticked, 'Warn me if iTunes is not the default player for audio files' stays ticked & the playlist on the L-side is recreated to its default (I previously deleted these).

What is going on?