I use CS4 for modding and cs5 for siggys which im currently working on right this second. Btw, I would sugest using a torent, but im not sure with that IP blocking law going around that every one is trying to veto. Try getting a torrent from a site by googling torrent site and hit im feeling lucky. So I hope I didnt violate any rules and hope I helped!
Yes if you go for Keygen from a torrent, make sure it has at least 100+ seeders, 5-10 positive comments, and etc.
Seeing as we can not post external links, I can't quite help out... I am sure this website has some, but I am new to it.