CPU Under clocked?

[Mr Bubble Smash]

I bought the computer with a 4.2GHz processor, it worked fine for a year.
But when i check "computer->properties" it only says it is a 3.4GHz processor when it used to say 4.2GHz.

Is there any way i can change it back to 4.2GHz?

 

[computergod]

Have you cleaned your computer lately? It could be down clocking because its getting hot. Is your computer custom or from a factory and what type of cooler do you have?

 

[Mr Bubble Smash]

I have cleaned the computer recently, it is a desktop custom built. Iam not sure what cooler i have.