Cf not running...

Completly uninstall your Game by using something like Ccleaner.
After that, download Crossfire again from the regular Download Mirrors and / or Alternative Download Mirrors from the website.
If these Mirrors dont work for you, you can try it with this Mirror.
Install Crossfire by ensuring, that Crossfire.exe, Gameguard.mon and Gameguard.des got full access through your firewall and turn your Antivirus program off for the Installation.
Also ensure, that your runing the Setup and the Gamestart as Administrator, if your using Windows Vista / Windows 7.
If these steps dont work for you, let my know, what Error you get and i'll help you solving your problem