system becomes slow and some times window becomes black

[MD TAMIM]

The system doesn't responds or sometimes on opening a new window,the screen becomes black and system becomes very slow.when normally working system is fast.the problem happens sometimes.The same problem existed before i upgraded my laptop with 2GB RAM to existing 2GB RAM.after few days it is showing the same problem.The laptop is 4 years old.Please help me...
Thank you in advance!

 

[Jared222]

"upgraded my laptop with 2GB RAM to existing 2GB RAM"

Do you mean to say you kept the old RAM or replaced it?

Does the problem occur when you run certain programs or anytime?

When the problem occurs, use task manager to see what processes are chewing up CPU and memory. Try updating drivers.

Does the problem still occur in safe mode?