How to reinstall video drivers?

[Richard]

I have Ubuntu 10.10 on a Dell Inspiron 1545 laptop.  The video worked 
sorta well  until I tried to change the driver to get it to work on 
Google video chat.  Eventually I got it to work but now the video is set 
at 800x640 and I cant get it to detect the monitor and change to the 
higher resolutions.

I've googled, and read and read and still cant find anything besides a 
reinstallation to correct my errors, whatever they may be.  So how do 
you reinstall the video system without a complete reinstallation?

Richard