Gmod Start / Connection Problem

My specs include

-Intel Core Two Duo 3.21 Ghz clock
-2 GB’s of DDR2 Ram
-NVidia GeForce 9600 GT
-Windows XP Home Edition


As I launch Garry’s mod, It would attempt to start up but fails. On occasion, it leaves the Hl2.exe Instance open on my processes tab of Task Manager. It started doing this after I experimented with a Duel screen setup. After I reset my Nvidia control panel, I attempted to start it and it started and stopped. On other occasion I get the, ‘‘Cannot read Memory (Some location)’’ Message after it opens and closes. I’ve used the command, ‘’-dxlevel 90’’ To force it to open (Which it does). Once its open, I have attempted in the past to connect to a server and a few seconds after reaching ‘‘Sending client info’’ It crashes. I also would like to note that once open, I reset it to my demensions and make it run in an window.

Any tips?
I’ve also re-installed.