Shoutbox

Hi
i clicked on a link stupidly from a friend on msn and got a virus.
i updated my virus protection since and think i got rid of it but it has damaged windows a fair bit and deleted a fair few files from my computer like dll files and now my windows is running very bad.
it is doing things like closing my start menu bar when ever i try to open a folder and closing the folder so i cant even get into anything like my documents or my pictures or even control panel.
This seems to be the only thing wrong now.
I am using vista

Any idea how to fix this wud be much appriciated.

Thanks