The current version of
Bootstrap can neither be compiled on
WinLess nor
lessc.exe as of writing. I found that these days the easiest is actually to run the Windows version of Node.js.
Standalone single .exe versions of Node.js are available. Go download the
less.js source and you can make yourself a "lessjs.cmd" with something like the following:
d:\utils\node.exe d:\utils\lesscss\bin\lessc %1