I have licensed Windows 7 CD and i have installed the same in my laptop.
Now one of my friend want to format her system and install Windows 7 in her laptop.
Can she use that CD, and if she uses, in future i can able to use the same again for the laptop??
If she purchases a separate license and product key from Microsoft, then yes. Otherwise both systems will likely run afoul of the Windows Genuine Advantage checks that give some teeth to the "one copy on one computer" portion of the Windows EULA.