Crashing on startup

Whenever I start Gmod, it stays on the preparing to launch gmod window for a while. Then it dissapears and the message comes up that hl2.exe has ecountered a problem and needs to close. (The one with the send/dont send options.)

I reinstalled Half Life 2, Episode 2 and Gmod but it still doesn’t work.
I also completely deleted my garrysmod folder before reinstalling.
My specs are:

1GB Ram
ATI Radeon HD2600 (512MB)
AMD Athlon 64 X2 5000+
And the latest drivers/DirectX.

Anyone got any solutions?