Yeah usually the sound level on turntables isn't too high so a preamp is needed. Another option is to get a phono-preamp/usb-interface that will amplify the signal and allow you to record it into your computer through usb. There's also turntables made with built in usb-interfaces like the Numark TT-USB. As for software, Audacity (which ASBO mentioned) will work great for doing this. But if you just want to go straight into your soundcard and don't want to buy a preamp, use the amplifier from your stereo system (assuming that if you have a turntable, you'd also have a receiver unit and speakers).