You might look into Sonar ...
www.cakewalk.com/sonar ...
You'll have to buy your own loops and other stuff. Eventually you'll want a nice sound card like:
http://www.m-audio.com/index.php?do=...=pciinterfaces
You probably don't need one of the 8 channel interfaces ... but you probably want at least a 4 in 2 out ...
Doug