Thanks for trying it, joebo! Yeah windows doesn't have the posix system calls that underly unix-like systems.
I don't have much experience with windows, and it's been a while since I used it, but I think fork() will work under cygwin. Running atop cygwin will probably also help with future incompatibilities.
I'm using wart as a way to help ease me into Common Lisp. I've had difficulty before reading CL code because the names of common operators are so different from arc's (the lisp dialect I know best). wart helps by putting it in familiar terms.