The game lags alot when there's alot of units (like when playing custom maps)

Is my CPU too old? Because it even lags when i point the camera to an area of the screen where there is very few units so i don't think it's my graphics card.

CPU: Pentium 4 3.4GHz (hyper-threading)
Graphics: NVIDIA GeForce 9600 GT 512MB
Windows XP

Graphics settings are set to low. Very few things running in the background.
Even normal games start out slightly laggy and it starts to really lag when theres more units in the match. It becomes unplayable on some custom maps where there is alot of units.

Lolwat,

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Q u o t e:
CPU: Pentium 4 3.4GHz (hyper-threading)

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Your processor is on the lower end. Dual core is recommended. Also, how much system RAM do you have?