Counter-Strike Anthology CD-Key will let you download, install and play all these different games through the Steam platform:

Condition Zero
Counter Strike 1.6
Ricochet
Day of Defeat
Condition Zero Deleted Scenes
Deathmatch Classic
Counter-Strike steamworks beta

This is the exact same product sold here: http://store.steampowered.com/sub/41/

We will send you a CD-Key within 12 hours of payment to the email used when paying via Paypal, this CD-Key can be registered on Steam.

Please note that in order to register this CD-Key on Steam, you will be asked to put in your Counter-Strike Anthology CD in your CD-drive. However, to bypass this check you can load the CD-protection image (~4mb) on a virtual CD-drive such as DAEMON Tools. The link to the CD-protection image will be in the email sent to you with the CD-Key.