If you are running Windows 7 and have less than 4 gigs of ram, upgrading to 4gigs or more MAY help a little.
Unfortunately laptops aren't very upgradable and that one is already 7 years old......
Mostly all you can do is try to optimize your operating system. Try http://www.piriform.com/ccleaner this is free software that cleans out temp files and directories. Another good one is http://www.iobit.com/advancedsystemcareper.html which has a free or pay version. (I use the free one). This software cleans up a lot of windows functions including the registry and can fix security problems with windows. One thing that commonly slows down systems is the anti-virus program. If you have Norton or McAffee, I'd delete them and just get the free Microsoft Security Essentials - its good enough and it doesn't slow your system to a halt. Defragging your hard drive is essential, make sure you do it at least every couple of months.
Personally, I buy cheap laptops and hope they last a year or two before upgrading. I'm on a Lenovo Second gen i5 with 6 gigs of ram right now that was 400 bucks last year.
I would recommend De-fragmenting your hard drive. In most cases, a slow computer is a result of hard drive issues. If that doesn't work, and you have backup CD's, you can reformat your hard drive, which will completely wipe it clean. A fresh start, basically. Just remember to back up all your files on a few CDs. If either of those don't work, then I think it's time for an upgrade. Computer parts just get old over time, and their efficiency lessens. Hope this helps -IP