A friend gave me his macbook air for reset factory. i have never done a factory reset on any Apple product so i don't know exactly how to do it. but off course there is internet and i have found the instructions. the problem is he has installed a Windows 7 too so it has both Mac OS 10.6.5 and Win 7. according to instructions after i restart the device i have to hold down Command and R buttons together which i did. but every time i end up in the same OS selection page. i tried different timings ; i hold the buttons sooner and later and even at the same time as restarting but it's the same result! so what should i do?