Computer crashes some time while running?

Hello!
I installed 1 GB of RAM today. It seems that it is correctly installed, but the only
problem is that my computer has , only one slot for RAM. So I put out the old RAM that is
512 MB and replaced it with new one that is of 1 GB . But now — whenever I play videos,
listen to music or play computer games– it pauses, and sometimes stops.
Is there any solution?
