win2k should have a telnet program built in; use that to connect to your OSX box. Once you're connected, you aren't using win2k anymore, you're using OSX (well, darwin really) so the commands aren't any different than they would be in a OSX terminal window: ps -aux will get a list of running processes, kill -9 (pid) will kill the process with the pid you give it. I'm not sure if you can use the open command to launch a graphical app, but you could kill it, then relaunch it back at the OSX box.
Actually I was asking for more specific examples. Like, I type 'open' and the IP address of my Mac from my PC telnet. But it says connection failed. I have the remote login option checked on my X machine too. Is there some other way like typing the machine name? is so, what is the machine name? is it the user name?
No, that is not the way to do things ;-)
Go to your, hmmm... "run" button, type "telnet ip-of-your-osx-box" and wait till you see the login prompt. Provide username and login and you'll inside your osx-box. And, no you won't have any graphical-windows or anything. No "open"-command. Nothing. Plain shell-commands will do. I.e.: "ps auxw" "ls" ...
IIRC the version 10.0.1 of MacOSX came with ssh. Since then telnet is disabled, but you can login via ssh.
Get the nice littele app "Putty" for Windows (Freeware) and try it with ssh. This should work.