Garry's Mod not starting - just opens then instantly closes

Hi,
I have quite a large issue with GMod 13. I just installed it on my Windows XP laptop which plays games very well, and all it does is comes up with the usual “Preparing to start Garry’s Mod…”, my desktop icons disappear for a split second, the Garry’s Mod logo appears in my taskbar, and then disappears again. Before, it came up with a DirectX Runtime error, so I updated it and now this is all that happens. I see this as quite an issue, as I do find Garry’s Mod a very good game (I have other laptops that I can play it on - but not very oftenly!!)
The laptop’s specs are below.

EDIT: I am going to try and install WinXP SP3, so don’t start complaining yet :smiley:

Thanks in advance for the help (hint, hint!!),
Aaron (Not Richard Carson as the pic may say :-p)

I was about to warn about the key, but I noticed that key just labels Windows
Anyways,
You could always reinstall or verify by going into steam, library, right click on Garry’s Mod, Local Files, and click on Verify game cache.