Gmod lags for almost every map, now. It didn't do this before.

[DarkIron112]

Hello, I'm DarkIron112- Long time Gmod 10 owner/fan.

I've got a problem that would typically ere on the side of hardware. When I load a map with any decent amount of textures, or NPCs, or anything that basically requires an application of the video card, I get horrible lag- far less than a frame per second. And I don't even have to move to face this lag.

It first happened on DarkRP maps- I had no problem running them, and then one day I did. Since this started I have undergone two software format/reinstalls.
My hardware:

Mobo - Gigabyte GA-MA785G-UD3H
Processor - AMD Phenom II X2 545 Processor, MMX, 3DNow (2 CPUs), ~3.0GHz
RAM - 3326MB RAM
Video - NVIDIA GeForce 8800 GTS (640mb)

What lead me to believe this is not a hardware issue (though that may not be the case) is when I loaded the map Cube 2.2... As usual, there was lag and I could barely move. Sick of it, I put every single video setting to its lowest- To a level I had lower than I had had BEFORE I upgraded from my Geforce 6100. The lag persisted, and I then came to the professionals for help.

If there is anything that I'm forgetting that you need, let me know. I would very much like to be able to play this game at full capacity again.

[WarriorXK]

Did you reinstall the drivers after the format?