Resetting my Dell Studio 1558

[PurpaFur]

I recently found a Dell Studio 1558 running Windows 7 Home Premium in the trash, and it works fine. I would like to do a full system reset to restore the laptop to factory condition. How can this be done? I have already tried pressing F8 on the startup screen, but all it would do is stop the loading bar. Then I tried leaving it for a while, and after 20 minutes it had done nothing. Many retries later I am still where I started.

Just a note, the computer keeps telling me that I need to get "genuine Windows Software" and other similar messages.

 

[Tmagic650]

Windows is not properly activated on this computer. You will need to get a retail copy of Windows 7 that can be properly activated, and do a clean Windows install. Go to Dell's support website to get the Windows 7 drivers. If you can see a Windows activation key sticker on the case, you might be able to use this site:
http://www.microsoft.com/en-us/software-recovery