The way mine is set up is it's basically a Kenwood stacker system (with seperate tape deck, turntable, amp etc.) basically the Line-out cable that usually plugs into the speakers goes into the amp's AUX socket. Then you run another cable from the amp's Tape Record Out (yours might be called something slightly different) into the Line-in on the PC (NOT the Mic, this is too sensitive so the sound will be distorted, also it's only in Mono). As for recording, change the recording input to Line-in in the Volume Control in Windows, then when you record from vinyl (I assume using Cubase) make sure you save it in at least 192 Kbps MP3 format (even higher if you have the hard drive space).
click here and click here for a couple of pics of how mine's wired up.