I bought a used Dell computer from a local university surplus store. The hard drive has been wiped. I did boot it up to bios and it appears to have everything else needed ... RAM, Graphics Card, et al. So, it should be operational. And the Windows 7 Pro COA stickers are still attached to the machine. Can't I do a clean install of Windows 7 on this machine ... free of charge? If so, what are the steps to doing that? I am a newbie at this stuff.