NEED HELP

I am having a game issue...
This just started recently, no hardware, update, or driver changes occured before problem started as far as I know.
My HL2DM runs fine as long as there are not a lot of players in the game, and smg's and ar2's arent being fired. If i am playing a 1v1 or something everything is great.
If I go into a pub (where theres lots of props being thrown or smg firing) I get major lag, almost like my game is skipping frames altogether.
It didn't used to do this. For ex. I could go on socialserver where there is lots of props/smg's and everything was fine. Now if I go on it is not even playable.
Seems to occur when props are being thrown or heavy fire. Makes everything laggy, grenades, crossbow, weapon switching, ect.
I don't have the best computer but it plays dm with power to spare.. usually 120-150fps
Dell Vostro Laptop 1500
1.6ghz Intel core 2 duo
2gb ram
nvidia 8600 GT
500gb 7200rpm seagate
1080p res screen
Windows Vista premium
I have tried new vid card driver, reinstalling the game, gcf defrag, reg fix, overall computer cleanup, ect.
I just reinstalled the OS maybe 1 month ago so its pretty fresh
Any help would be appreciated! Thanks

Sound like laggy Socal servers or internet in general.
You could google around for an autoexec file that allows Tick/rate adjustments on the fly.
Turn on your Netgraph and see if you have lots of loss or choke.

Probably choke on some servers.

And Socal is laggy sometimes, esp here on the East, with lots of folks in there.

if you're not running SLI dont use any nvidea drivers past the 182.50 release. they cause me major issues, and from my research im not the only one. try that first. also try resetting your router and modem, thats always a nice quick fix for internet issues.