haha, ok dude. i had pretty much the same issue as you. its your fail graphics chipset.
the 945gma is absolute garbage.
here throw this in your startup commands for gmod.
-dxlevel 90 +mat_forcehardwaresync 0 -windowed -dxlevel 90 -w 640 -h 480 +mat_dxlevel 90 +r_dynamic 0 +r_threaded_particles 1
i searched for a long time before finding this code for my laptop. fixed mine, but not my friend, but he had a 965gma so that could be it.
it crashes without windowed, so just set the 640 and 480 to something more manageable like 800 and 600 or if you have the screen real estate maybe 1024 and 768 or higher.
hope this works for you.