Before you can install Call of Duty 5 you'll need to find the serial number that came with the program. Call of Duty 5 requires that you enter a unique serial number before using it.
If you've lost your serial number, there is a way to find it as long as Call of Duty is still installed. You might be able to find your CoD 5 serial number if you've uninstalled the program but only if the serial number information was left in the Windows Registry.
The Call of Duty 5 serial number is actually more of a product key than a serial number but as with most software, the terms are usually used interchangeably.
Assuming Call of Duty 5 is still installed, the easiest way to find your unique serial number is by using a free product key finder program. Product key finder programs automatically search your computer for the product keys and serial numbers that your software programs store in the registry.
Most product key finder programs are designed to find the product keys for operating systems like Windows XP or Windows Vista but some of them find product keys and serial numbers for several other programs too, including Call of Duty 5.
The product key finder program that I've confirmed will find your Call of Duty serial number is Magical Jelly Bean Keyfinder. If it doesn't find your serial number, give some of the other key finder programs a try that I linked to a few paragraphs back. Be sure to let me know that it didn't work for you so I can keep this page updated. Be specific as well - if a key finder program worked for Call of Duty 5: World at War but not Call of Duty 4, let me know.
Important: You may have come across Call of Duty 5 keygen programs or other kinds of Call of Duty 5 cracks but keep in mind that these are not legal ways of obtaining serial numbers or product keys. The only legal way of installing this program is by using a valid CoD 5 serial number obtained through a legal purchase of the software.