I've done quite a lot of this, with a USB turntable (an excellent purchase). It came with Audacity software (free & open source, even better), which I already was using and which, IMHO, is actually the best software to use. Audacity can also filter the pops & clicks, but it's actually quite hard to get all the spikes off the recording - in the end I learned to just live with a few. I record with Audacity, clean it up, export the file to WMA then use more free software called Switch, to convert to MP3. I could simply export to MP3 in the first place, but why do it the easy way when there's a more interesting way, right??

Basically, with Audacity, if you can play it through the PC speakers, you can record it & convert to WMA or MP3....CD, DVD, Internet radio, line in...whatever. Which is quite cool.