Without, I'd recommend the Cambridge 640c wholeheartedly.
With, I'd look first at the Pro-Ject Phono Box USB, though I've seen recommended the ARTcessories USB Phono Plus, which has more facilities (headphone monitoring for example) and one by Terratec. You might find you get just as good quality with a dedicated phono stage (see above) and a quality 2 x phono to mini jack into the PC, however.
Whichever solution you use, make sure you have a proper audio recording facility on your PC - XP didn't have one, and have never looked on Vista. A USB Phono Stage may come with the requisite software, but a colleague suggested one which splits tracks automatically - will ask which one he uses
Edit - lpripper or lprecorder - www.cfbsoftware.com.