Basically I reinstalled Windows today under the impression that my iPod would act like a memory stick and transfer all the music over to the "new" hard-drive (so in effect, transfering it all to a new computer). However, installing iTunes and connecting the iPod didn't transfer all the songs, only the purchased ones. My others which are almost all from CDs (apart from the naughty illegal ones) haven't transfered and are still on my iPod. I'm guessing pressing Sync Songs on iPod will delete all my other music from the device. Is there any way of transfering the remaining music onto the computer?

To put it simply.. no. The iPod won't act as a hard drive for your music.

Easy way to recover them all is to download and install:

Winamp

Then install the the ml_ipod plug in

With your Ipod connected, wait for it to appear in the left hand panel.

optionally click on Winamp, press "Ctrl + P", then under "Ipod Support" click "Transfers", click the "Download" tab, and change the naming scheme and local file you want all the MP3's to get on your PC. (IIRC the default is to shove them in the My Music folder).

Right click on your Ipod in the left hand panel, select "Ipod tools" then select "Copy to hard drive all songs not in ML"

Go make yourself a brew or grab a beer, watch some TV and when you return it will hopefully have copied everything to your PC.

(You will need to enable "Disk Mode" in Itunes for your Ipod for any of this too work).

See, this is why I like the Microsoft Zune, the (granted, proprietary) software actually allows you to synch music and video from and to your Zune from and to any computer.

just download the sharepod software - works really well