I use Anvil Studio (free version) for making backing tracks (Bass & Drums) as its very easy to use.
I don't use an interface, as such, but put my input from a Digitech Multi FX into a small mixer and into the mic socket on my PC. My main recording software is Mixcraft (about £50) which is very nice but has a few quirks. Monitoring tracks is a work of art as it does record in real time (unlike most recording software) but monitors with a bad (1/4 sec) latency on the monitoring. This is no problem if I'm mic'ing up an amp or playing my acoustic, but for direct electric is a pain. At least I can mute the recording track. It does have built-in pitch correction although its not strong enough to correct my voice(!) I have just added Beatcraft for better drum sounds and easier looping. Not tried it in anger yet but its looking nice and makes me pick up the bass.
My PC is an AMD based Phenom 9600 with just 2gig of ram (must upgrade) so I have to be a bit careful about leaving 'net stuff off when recording. I have used Audacity (free) in the past but that puts the latency on the track instead of the monitoring. Not a disaster as you can easily nudge the new track into line to get it right.

Brian
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I pick up my guitar and play
Just like yesterday

Guitarist with The Silver Hoarde. Geriatric Metal for your weddings and wakes.