I just happened to be reading about "Alcohol 120%" (
http://www.alcohol-software.com) and saw this feature:
-Store your most used or important CDs as images on your computer and run them at 200x speed from up to 31 virtual CD or DVD drives!
I wonder if you could use that as a "virtual live CD" for DSL, Knoppix, etc. You would run much faster, would not have to "install" the distro to your HDD to test it out and your MBR would be safe.
Is that an interesting idea? I don't have Alcohol 120% but if I did I would try it out with DSL.
Cheers.