[entwisi]

remove any 'downloaded' copys of the installer, clear your browser cache (to make sure its not caching a dodgy copy) reboot and then download it again from iTunes.com.

There are other apps that will load/sync with iPods so you could also try one of these

Anapod Explorer™ iPod Software, iPod Backup, iTunes Alternative, iPod Transfer, iPod Manager, iPod Management, iPod Explorer, iPod Utility, iTunes Replacement, iPod Copy, iPod Freeware, iPod Managing, PC Software, Windows Software, Windows Vista Soft (use the trial version to get sorted today)

EphPod - iPod for Windows (and Linux) :: HOME

There is also Linux apps that can sync but you probably guessed that already