Audacity will do it.
CTRL-A to select the entire track, then "adjust tempo" from the edit (IIRC) menu. Use google for a couple of other different ways to do it in Audacity.
Download from here:
http://audacity.sourceforge.net/download/
Yes, free....
There are some other threads on "slow down" tools here in TB, you can search for them, I forget what the alternatives are.
- Mike