I just got a used macbook pro and i was having issues with airport. So I reinstalled mac os x leopard. Ever since then the computer has been acting very slow, with the beach ball spinny thing and the typing is delayed sometimes. There are also a ton of error messages keep popping up in console, like a lot of them. Please help.

The error logs in Console.app will give you clues on why your Mac is slow. You can also look in Activity Monitor to see what if any app is using up the CPU and/or RAM.
http://thexlab.com/faqs/checkconsole.html
http://thexlab.com/faqs/faqs.html