Assuming you only want to record 1 or 2 tracks at a time any old multitrack recording software should do. I use an old copy of Cubase on the odd occasion I want to do something like this.
Kristal would appear to be free and should do the biz, but I've not tried it (praps I will, hmm...).
Anyway - it's all pretty straightforward, the only slight difficulty concerns latency. That's the inability of the computer to sync input and output for monitoring purposes when overdubbing. In practice it's not that much of a problem cos you can easily shift the tracks in time after recording.
If you want multitrack input and decent monitoring then it's dedicated hardware you need. Megabucks.
<edit> Just playing around with Kristal now. It is free for personal use and appears to do what you want. The demo track is loud.
