Having lag problems on my desktop and wondering whats causing it.

[BalrogOfMorgoth]

ok so i have a laptop that runs gmod and it has its lag spikes but in single player for the most part it runs pretty smooth, it has a 1.7GHz amd dual core processor, so my problem is i have a desktop i just bought (A Dell Vostro 200, not the mini)
and it has a intel pentium 3.8GHz dual core and it lags Gmod really bad online, but it runs smooth in single of course, except on gm bigcity. my question is what is causing this because i know its not the processor so is it the ram or should i get a graphics card? If i need ram i have already bought 4 gigs so im at 6 gigs now, but i think i need a new graphics card because gmod will actually crash when joining a server with big city. If i need a new graphics card if you guys could give a list of compatible ones for my computer i would appreciate it very much, price isnt a big deal as long as its not more than $250, i would like a graphics card that could run games like planet side 2 and stuff like that. Thank you very much in advance for any help given! oh and i have a 300w power supply ask any other hardware questions i have left out.

 

[TastyPony]

Do you have a nVidia card? If so, do you have V-Sync on? If you don't just right click on the desktop go down to nVidia Control Panel and search through the options till you find V-Sync and enable it. If that doesn't work or you just don't have a nVidia card try re installing G-Mod see if that fixes it. If that doesn't help well might just be (as you said) that you need another GPU. If you need any suggestions I'll see what I can do.
Welp good luck.

 

[BalrogOfMorgoth]

Do you have a nVidia card? If so, do you have V-Sync on? If you don't just right click on the desktop go down to nVidia Control Panel and search through the options till you find V-Sync and enable it. If that doesn't work or you just don't have a nVidia card try re installing G-Mod see if that fixes it. If that doesn't help well might just be (as you said) that you need another GPU. If you need any suggestions I'll see what I can do.
Welp good luck.

i don't have nvidia, and the computer did this with vista to but i think i just need a new GPU. Do you know of any compatible with my rig? I am usually pretty good with computer hardware but the realm of graphics cards is a foreign land to me lol thanks in advance