dropped MacBook Pro, still working but it freezes

I recently dropped my MBP, it fell from my table to the floor in about 1.5 meters

I picked it up and it was still on but the screen behaved like it was in an out of range frequency. I forced a shut down by pressing the power button. I tried starting again and it did start but was slow as ^^&$. Otherwise it looked OK from the outside, no bigger damages on the outside.

Afterwards I tried to re-install the Snow Leopard but I saw that my HDD is dead. Recently I got a new Toshiba 500 HDD and replaced the old one. I did a clean install of Snow Leopard and it installed just fine, but now its behaving strangely:

First it takes longer for the MAC OS to startup & from time to time the programs seem to freeze but the cursor moves without any problem except for it doesnt respond to its actions. Any ideas what might be wrong?