Macbook Issues

Lately my macbook has been really flaky. I took it apart to fix a broken piece that was depressing the disk drive (result of a fall), and everything was working fine before and after this. Then suddenly the battery wont charge or be recognized. I took it into the apple store today and they replaced the battery because it was "bad"
I got it home, and it still wasn't recognizing the battery. It would charge it for a minute then just cease to recognize it. I installed the battery updates, and did a fresh install of Leopard. Still no go. What is going on?

Instead of making a new thread, does anyone know how to delete previous systems? I had a kernel panic and had to reinstall tiger with my macbook CD's, and that took up 20 GB, then i just installed Leopard and thats another 5GB. How do i get this space back?

If anyone could answer either of these questions, it would be greatly appreciated.

 

I tried resetting the SMC, thanks though.
When i took it apart i was careful not to unplug anything, but I will take it apart again and check the connections. There is a screw on the back near the vents that i am worried about. It is stuck and wont come out, and i tried magnets. I guess i will need to try superglue.