Help to remove an old directory from google search results

I was using xoops for one of my sites. Now I ceased using xoops and deleted the whole xoops directory. Even after 3-4 months google is still showing those non-existent pages.
What is the best way to remove those from google search results with out affecting my other pages?
(I am using googe sitemap)

 

use robots.txt

User-agent: *
Disallow: /xoops/

 

But, xoops directory doesnt exists now.deleted from the server several months ago.

 

I am glad to hear you took down Xoops. It can cause redirect problems.
As for removing the urls,
http://www.google.com/webmasters/remove.html should have the information you need.