Garrysmod Crash when pressing "Cancel"

When I want to test a gamemode of mine, I sometimes forget to set the multi-player options to create the server as my gamemode, so it ends up as sandbox, so I press cancel, because i have noticed what i’ve done, and it freezes, goes back t the main menu, then the windows error sound pops up, i cannot do anything, Ctrl+alt+del does not work, and the start button does not work. So i have to press the restart button.

I am running with Windows XP Pro; Nvidia 260GT, 4GB RAM, 500GB Hard-drive memory

Well that’s pretty weird if your whole computer freezes up, XP may be the problem, but probably not, and your computer’s specs shouldn’t be a problem. Only thing I can think of would be malware, not that I have had any problems with that in a long time.