Then, use whichever your preferred VNC client is on the Windows machine. If you haven't used VNC before, take a look around http://www.versiontracker.com on the Windows software section for a decent VNC client.
If you have Tiger, you don't even have to install the VNC server. Just make sure Apple Remote Desktop is enabled in the Sharing System Preference, and check the option that says "VNC viewers may control screen with password" and specify that password. The Apple Remote Desktop VNC service always runs on port 5900 (Display 0)
Then, use whichever your preferred VNC client is on the Windows machine. If you haven't used VNC before, take a look around http://www.versiontracker.com on the Windows software section for a decent VNC client.
You know, I have used the VNC server that comes with Tiger, but for some reason it doesn't work as well as OSXvnc. It's kind of basic also compared to OSXvnc, IMO.