This is part of the Diet-PC Project. See below...
From the site:
"Although DIET-PC will run on 80386 and up, it is really intended for Pentium-I or better with at least 32 Mb of RAM. DIET-PC on new hardware will outperform most commercial thin clients for a comparable price."
Søren Schimkat has successfully compiled RDesktop on Win32 using the Cygwin environment. The compile is apparently very easy; use the following command line:
ln -s /usr/bin/gcc /usr/bin/cc