It's running slow

i have the basic 2.2 ghz core 2 duo. mbp.
I haven't had any problems with it until this last saturday. The computer does everything slow now. As i am typing this their is at least a 3 word lag between my fingers hitting the keys and it showing up on the screen. The mouse is also really jerky now and before it worked fine. Does anyone have any ideas, on what could increase my performance. Also, i am still running osx tiger.

have you checked the activity monitor? Applications -> Utilities -> Activity Monitor

If you say it is laggy it pretty much sounds like the CPU is at a 100%. might be because an application crashed and doesn't respond anymore. Or another app is using up a lot of RAM - or all RAM - so that your MBP started to swap data. Again, that would slow it down. Shouldn't that much, but it's a start...

Did you do a reboot since then?