Problems with Gmod 13, is it my computer?

[ASSiDxRAnE]

So 12 ran fine on my computer, but 13 is terrible. It lags like crazy at only 12 FPS, and parts of textures just disappear at times. i don't know why, but if it's hardware, these are my system specs for anyone who can help me:
Graphics card is an ATI Radeon HD 4200
Processor is an AMD athlon II X4 640 3.00 GHz
Windows 7
4 gigs of RAM

So any help would be greatly appreciated.

[MrBacon]

reinstall verify cache change settings

[ASSiDxRAnE]

[QUOTE=MrBacon;38183080]reinstall verify cache change settings[/QUOTE]

Thank you so much, It doesn't run perfectly, but it's soooooooo much better than it was! I really can't express the amount of thanks I have through text.