I think there is a typo in prng.lisp.
"sb!win32" does not designate a package. I 've changed it to "sb-win32" and it works on my Windows 7 platform (amd64, sbcl 1.0.55).
Hope this helps!
Fix a typo (I guess?) - sb!win32 does not designate a package. Change…
… it to sb-win32 and it works!
Thanks for the fix!