>I tried VNC, but it made my Linux box hang on boot. However, I later realised I never set a password in the VNC server, so it may be the reason for my problems. I haven't had the need to try again, so I didn't.

I've got VNC up and running, using the RPM that came with Mandrake, plus a few tweaks.

>If you do find an X-Server for Windows, let me know! I didn't find one! But I admit I looked for a free solution, since it was purely for the fun of trying it - not for business reason.

Without doing any research, I just assumed there was an XFree86 port for Windows. I think OS/2 and possibly Mac have one. I'll stick with VNC. According to the docs, it's based in part on the X server code anyway.