it is free and open and it can do a good job as a multitrackptaperecorder as long as you do not need professional Realtimerecording and flexible Routing for FX etc.
Audacity runs well in Windows, for the more sophisticated Stuff i recommend Mandrake Linux 9.2 (CD-ISOs for Installation are downloadable for free) plus the Apps from this page:
Cubase SE is pretty good and is pretty affordable for a steinberg product, 100$ usually. It's got some good stuff like a very useful plethora of effects and a nice equalizer and mixer levels and VT Instruments if u want to incoporate Drums into your guitar riffs. I suggest it, just save alittle and it's worth it. Hope this helps.