http://www.the-midfield.com/ipod.aspx

Here you will find all you need to update your 1st/2nd generation Windows iPod, and to convert your Mac 1st/2nd generation iPod to Windows. The only file you need is the 1.30 WinniePod Updater. The updater can perform both a 'restore', which will format your iPod hard-drive to windows and update it to 1.30 firmware, or an 'update' which updates Windows iPods to 1.3 without formatting the hard-drive.

I've tried this with my Ipod and I am happy with the result.