If you use iTunes with an iPod on XP (and maybe other Windows versions) do not upgrade to v10 without reading
this first.
The iPod service in 10.0.0.68 is broken and will not start. This means you can not sync your iPod. Apple have not yet released a fix for it.
I know these instructions work because I have just done it myself.
Before installing v10 back up the "\program files\ipod" directory.
Install v10.
Click the "Ignore" button for the "iPod Service failed to start".
Rename or delete "\program files\ipod".
Restore your backed up version.
Start iTunes
If you have already upgraded and don't have a copy of v9, there is a link in the discussion above to FileHippo where you can get 9.2.1