Problems syncing iPod Classic

My old computer died,have an external hard drive that supposed to have backup files,well maybe...Anyway,tried to backup my 7294 items on new computer running Windows 8.1 with newly installed iTunes and my account.Most of my music library is not iTunes purchases,but of the 2342 or so iTunes purchased only 894 show up.I tried to find and redownload as Apple says one can and not successful.Have 5 newly purchased songs that wiil not sync to My 160gb Ipod classic,along with everything else,plus they don't show in Recently Added menu.Bottom line, I can't get all of my purchases or iPod to sync{it will sync recently played but not anything new].Any help here?