All of Microsoft's operating systems require valid product keys to be entered during installation. Having a keygen program that creates CD keys could save you lots of money, especially if you've already paid for Windows 7 but have just lost the installation key.
Product keys created by Windows 7 keygens are NOT legal product keys. The only legal way to obtain a product key for Windows 7 is by purchasing the operating system yourself or by contacting Microsoft directly to obtain a replacement key.
Windows 7 keygen programs go by several different names including product key generators, serial number keygens, CD key makers, license key generators, CD key creators, and CD key extractors. Whatever the name, all Windows 7 keygens create free, unique product keys for use when installing Windows 7.
No matter what Windows 7 keygen you use, or where you download it from, using a product key other than the unique one that comes with an individual, legally purchased copy of Microsoft Windows 7 is illegal. Using a product key not issued by Microsoft is a violation of the agreement you make when you use Windows 7.
Requiring a valid, unique product key is one way that Microsoft ensures that each copy of their operating system is used only once and that each customer is paying for each copy of Windows 7 they have installed.
If you have a legal copy of Windows 7 but you've just lost your product key, try a free product key finder program to locate the key from your currently installed copy of Windows. This is a perfectly legal way of obtaining a Windows 7 product key because it's the same one that was used during the last installation of Windows 7 on your PC.
Note: If you need specific instructions on finding your Windows 7 key with a product key finder, see my How To Find the Windows 7 Product Key Code guide.
I obviously can't provide you with links to the various Windows 7 keygen programs available today since the product keys they create are not legal. If you can't retrieve your Windows 7 installation key with a product key finder program, then my only recommendations are to request a new product key from Microsoft or legally purchase a new copy of Windows 7.