My macbook getting stuck and running very badly

My macbook (unibody aluminum model late 2008) is running slowly, getting stuck and not respondings alot! I upgraded the system to os x snow leopard but that didn't make it better.

What's the matter?

Note: more iformation about my mac:

Model Name: MacBook

Model Identifier: MacBook5,1

Processor Name: Intel Core 2 Duo

Processor Speed: 2.4 GHz

Number Of Processors: 1

Total Number Of Cores: 2

L2 Cache: 3 MB

Memory: 2 GB

Bus Speed: 1.07 GHz

Boot ROM Version: MB51