Need Help With Opposing Force and steam

[kiwii]

So I found my old Opposing Force cd cover. the disk is gone however But the cd key is still intact. but i cant register it on steam it just tells me its invalid?? What am I doing wrong here? Do I have to install it the old fashion way or just download it from steam with a legal cd key? that would be all. Thanks :cheers:

 

[ytinupmi]

if you have a half-life cd-key use that, it will give you access to opposing force.

 

[Xac493]

I wish you could use OPF cd keys too... I lost my HL cdkey but i still got my OPF one .... I wish hl2 comes out sooner. I got no games to play....