Mirza i was having the exact same problem a few weeks ago, and after searching TONS of shites, and posting here.. i think you're best bet is to go with seg's suggestion.. use conditional comments. the only thing you could try is one of the so-called "holy hacks" but depending on what you're doing.. those often don't work for IE7.. so you could still be SOL..
some of the fixes though depend on what you're doing.. some awesome sites that i've found have been:
csscreator.com
www.positioniseverything.net
www.alistapart.com
first one is a forum, and your pages will have to be standards compliant for them to really help you.. but maybe you're already there.. :) and either way they have good info. the other two are big name css sites.. good luck! and IE blows!