Thanks for all your suggestions, even though I dont think my problem was fully understood
iPods are used as Hard drive storage as well as being music players, I had been using my iPod as storage but my itunes-uploaded music had been wiped(after being plugged into a freinds iBook!) so I wanted to upload all of my music via itunes back onto my iPod without deleting the data stored on the HD section of my iPod...
I bit the bullet and went for it, my iPod updated/sync'd after hours of 'syncing' and all of my data on the HD was still there at the end.
So, to answer my own question: NO, SYNCING YOUR IPOD WITH A PC DOES NOT DELETE THE DATA STORED ON THE HD SECTION OF YOUR IPOD(but does obviously overwright all existing itunes-uploaded music from previous sync/pc)
Problem solved