I had the same problem as you guys and yes holding the shift key does work very nicely but after I fixed the Itunes problem I found I was having problems in other programes. I got an error that said "error 1606 can't find network 0 ". I found that a prog had changed all my settings for My Music, My Pics and My vids to 0 in the registry.
Itunes could not find the My Music folder because the default had been changed in the registry. I had to go into the registry and change all of them.
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\User Shell Folders
All the entries are "name of folder" REG_EXPAND_SZ %USERPROFILE%\My Documents\"name of folder"\"name of subfolder"
These were all set to 0 so I changed them to the above.
You can download a prog off Microsoft which will fix My Pictures but I had to change the others manually. The prog is Microsoft fixit 50356.msi.
Hope this isn't too confusing you can e-mail if you need help with it all.