Command & Conquer
Command & Conquer The Covert Operations
Command & Conquer Red Alert
Command & Conquer Red Alert Counterstrike
Command & Conquer Red Alert The Aftermath
Command & Conquer Tiberian Sun
Command & Conquer Tiberian Sun Firestorm

Or less?

http://www.commandandconquer.com/collection/

The original C&C + Covert Operations is called C&C Gold, which was released for free.

Red Alert was released for free when EA announced Read Alert 3, but I don' believe it included the expansions.

Tiberian Sun and Firestorm were released for free together when EA announced C&C 4.

These used to be available directly from EA, but I'm not seeing the links anymore on the new C&C site (probably because they're releasing a new compilation pack of all the old C&C games, so they don't want to emphasize that half the games are already available for free). But the games are still available on some third-party sites:

C&C Gold: http://compactiongames.about.com/od/freegames/p/cc_free.htm
Red Alert: http://compactiongames.about.com/od/freegames/p/ccredalert_free.htm
Tiberian Sun: http://compactiongames.about.com/od/freegames/p/commandconquer_tiberiansun_free.htm

This is Origin. I don't prefer it. They are releasing a new compilation pack? Damn i just bought,

Red Alert 2
Red Alert 3
C&C 3
C&C 3 Expansion
Generals Deluxe

It doesn't work on Windows 7 64 bit. The unofficial patch is a stand-alone installer but no videos included. So currently i won't be able play.

What doesn't work? You'll have to be more specific to get a solution for the problem. :)

I think this is the site that offers some of the games, like the original, Red Alert, and Tiberian Sun, for free.

http://www.fileplanet.com/55413/0/section/Command-and-Conquer-Series

strategy informer also has them i believe (along with rise of nations, area 51 and some other stuff... but dont quote me on that!

Or fewer