Hello,
I've got a Dell PC with Mac OS X Leopard installed, and an identical Dell PC running Windows XP.
I login into the 'mac' from the PC using PuTTY and this successfully gets me a terminal window up while another person uses the 'mac'.

However, how can I do the same thing, but get the GUI interface instead of just the terminal window?

I've used TightVNC on the PC to control the desktop of the 'mac', but this prevents someone using the 'mac' at the same time.

Is there any way to do this, perhaps by launching the GUI from the terminal by typing in some command?

Or perhaps by using some kind of GUI-login version of PuTTY?

Thanks, I've looked all over for this, but the posts I've found talk about controlling the desktop using VNC, rather than having two simultaneous 'GUI logins'.

I don't think so.

use logmein for mac

What you're looking for is a terminal server type solution for os x.. there is iRapp but it's commercial, and I seem to remember there was an opensource version that did much the same thing, but I can't find it right now.

On any other *NIX solution, I'd suggest installing an Xserver on your PC such as eXceed. I don't know if you would be able to do that with your Hackintosh if you had X11 installed on it as I've never experimented with it.

I'm also not too up-to-date with Leopard Server's capabilities but perhaps it will support a better mechanism.

Honestly, I suggest my favorite solution: a 2-liter bottle of Coke and google.