Own them both but need to find them, I remember activating was a pain hopefully I have activations left...
Crysis 1 only had a CD check. Crysis Warhead had limited activations, though you can use the de-authorization tool put out by EA to reclaim an activation. You can find it here http://activate.ea.com/deauthorize/
. Click on the Crysis Warhead box art and it will download it.
If I'm not mistaken, the game had 5 activations before you had to call support, but they eventually moved this to 50(I think). If you've installed the game on your current system without reinstalling your machine you can actually reclaim an activation. I can't remember if you have to have the game installed before doing this or not. Either way try it out. It tells you how many activations you have left at the end of the de-authorization wizard.
One thing to remember when installing is to make sure to patch them up to the current version. My mod might not work correctly otherwise because some of the files don't exist without the patch. Crysis Warhead also had an annoying software piece that would check the release date for the game and the date you're installing it to ensure it wasn't a stolen copy. That software tries to reach out to a server that no longer exists. After patching the game, this software was removed. Without patching it will never let you play.