How can i avoid the indexing of forum pages but allow thread pages?

Let me explain,

i don't want search engines to index forum pages such as:
http://forums.digitalpoint.com/forumdisplay.php?f=50

i want them to crawl through forum pages and index all threads such as:
http://forums.digitalpoint.com/showthread.php?t=1303772

Is this possible and how can i do this?
If i disallow the forum pages, will the search engines continue to index the threads?

 

This is exactly the question I have.

Its simple to disallow any file or directory, such as:
disallow: /forums/
disallow: /forums/somefile.php

can it allow or disallow urls using some predefined pattern?

I mean, I have some urls like this:
/forums/index.php?act=Post&CODE=02&f=15&t=13&qpid=15
/forums/index.php?act=Post&CODE=02&f=15&t=13&qpid=85
/forums/index.php?act=Post&CODE=02&f=15&t=14&qpid=16

and I do not want bots to index them, and I want to disallow the urls, which start on:
/forums/index.php?act=Post&CODE=02 ?

if I write the following in robots.txt
disallow: /forums/index.php?act=Post&CODE=02
or
disallow: /forums/index.php?act=Post&CODE=02*

will it work? or it will disallow the whole /forums/ directory or block /forums/index.php file totally?

I do not want to test it till I'm not sure, while google has indexed more than 35000 urls from my webpage and there is a big threat in modifying robots.txt.

 

Simply disallow: /forumdisplay.php?f=*