Used iPod Classic 80GB Only Syncing Purchased Music

My iPod classic 160gb recently got wet and broke, and I purchased a used 80gb classic off of Amazon. It works fine except when I sync it with iTunes it will only sync the songs purchased through iTunes, not the ones purchased from Amazon or burned or anything else. I get different error messages, ranging from:

iTunes could not sync to Owners iPod, file not found

iTunes could not sync (song name) error code (keeps ******* changing)

iTunes could not sync, duplicate file found

Windows will also randomly tell me I need to fix the driver, and after I fix it, it will tell me it again upon trying to sync.

Steps I have taken:

Updated iPod software

Updated iTunes software

Restored iPod twice

Tried different cables

Tried different ports

Tried manual drag and drop

Restarted computer

Turned off Firewall

Checking Properties

Any help appreciated, if this doesn't work I'm going to sell this and just buy a massive SD card for my phone because this process has been very frustrating.