Here are some programs that might be helpful with playing the .wav loops (all are free unless otherwise noted):
AnalogX Scratch - One of my favorites. You can scratch a mono .wav like a record and change the speed while the other .wav plays. Also has a function that allows you to record your scratches in 16-bit mono .wav files.
Cool Edit '96 - This one is also pretty good. This one lets you record off your computer's mic and adjust the speed, add echo and do many other effects. This is the unregistered version, you can use two effects for one session. To use them all at one session, you'll have to buy the full version, the unregistered version will get the job done though.
MixPEG - Another great program. Lets you chop up, mix, and change the speed of .mp3s. Only bad thing is there's not a feature to record them. You'll have to use a program such as Cool Edit, or hook up a tape recorder to your computer to do that.