Garry's Mod Multiplayer Crashing

-nVidia 9600 GT
-1.8 Ghz Processor (Don’t even.)
-512MB of RAM (Again, don’t even.)
-Windows XP

When I connect to any server on Garry’s Mod, it loads normally. But when it finishes downloading everything, the game completely freezes, and I either task-manager it, or restart my computer to get out of it. This has really been bothering me, and I really do want to play Garry’s Mod on multiplayer.

(Also, does anyone else here find de_school creepy as fuck?)

1.8Ghz and 512MB ram seem to explain this.

Care to elaborate on what I can do to help it [possibly] work?

i have the same problem when i go to a server everythings fine but when i get shot or something or somthing blow up it lagges like hell then does the hl2.exp thing has stoped woring how do i fix that?