Problem with my cpu not using both of its cores

I have bought a i3 2120 with a gigabyte Z77 only a few months ago and when I launched blacklight retribution today a warning message (came up that said that my cpu does not meet minimum requirements (dual core) to play). I opened up speed fan and task manager and my cpu was fluctuating between 20% - and 100% on idle. I already tried installing drivers and it doesn't work. 

Can someone help me fix my problem please.

start menu, search msconfig, enter, boot tab, advanced settings, change the number of maximum processors to 2 or 4 depending on if you have hyper treading on

 

already did that.

Well, if the CPU is working properly, I'd just ignore the warning. If the game doesn't start, I'd double check the BIOS settings (make sure both cores are enabled + optionally hyper-threading) and submit a bug report if problem presists. Also, what process is taking up the idle CPU resources?

You could try this:

Access Task Manager.
Choose the Processes tab.
Right-click the process associated with the problem application.
Select the Set Affinity command.
From the Processor Affinity dialog box, set one of the CPU check boxes.

If your cpu isn't functioning properly, then you're probably going to have to buy a new one...

use SIW or device manager to make sure only two cores are showing up. if both are, dont wory about it.

if there is still a problem, make sure there is no bios update. if not, its probubly a bad cpu.

 

i had a gigabyte board with a 955be (3.2ghz quad). in windows, it was showing 3.2ghz on core 0, and then 1.4 ghz on cores 1 2 and 3. so yeah, a bios update might fix it :)

highly doubt its a bad CPU that is nearly unheard of, more likely, bios update needed, bios option, or bent Mobo pins