Windows 7 can be upgraded from windows XP and Vista but what if you accidently removed your XP or Vista and still you want to install your windows 7 with upgrade media. Here are very simple steps you can follow and install your windows 7.
1. Install a completely clean Windows 7 bypassing the activation process.
2. Make sure that there aren’t any pending Windows Updates that will require a reboot.
3. Go to Run Menu and enter regedit.exe
4. Navigate to the registry key:
HKLM/Software/Microsoft/Windows/CurrentVersion/Setup/OOBE/