IPod Classic Sync Issues - Tried everything!

My old iPod classic would not sync with iTunes, It would maybe sync the first 30 songs out of my 2000 and then iTunes would freeze and no other songs could be synced. After messing around with the iPod I decided to buy a new one, which I did. It has the exact same issue, I cannot sync all my music from iTunes. I've tried other programs like SharePod but they also just seem to freeze half way through. Also, I opened iTunes after an unsuccessful sync and most of my music was gone. I downloaded it all again and attempted a sync with SharePod, guess what? It was all deleted again! It's a second hand iPod so Apple can't help me.

I have a Windows 7 PC running on a 1.8Ghz Core 2 Duo with 2GB of RAM. Running latest version of iTunes, tried reinstalling it. Also restored my iPod several times.

Can provide more info if needed.

Please help, it's so frustrating!