Put Leopard on my Macbook....now having problems

First, I am a new Mac user. I bought a refurbished Macbook from Apple a month ago. 1.83 ghz and 2 x 256. The Leopard disk they sent me didn't work, so I finally got one a month later. I put it on and now Firefox keeps closing, the computer is freezing (or the colorful circle will not go away) and at times I can't type anything in the URL bar. Has this happened to anyone?

I also have a question about Tiger. Is there a way to uninstall this now that I have Leopard on? I did not see an option for this when I installed Leopard. I am wondering if this has anything to do with my problem. Please advise.

IIRC, installing leopard in essence replaces the parts of previous systems with the leopard versions.

also, you are not alone with the problems with leopard. i've reinstalled it three times on my machine, and i think i almost got it right the last time.