Installing windows and restoring laptop to factory default settings question! Dhunt! Dhunt! Dhunt!?

Ok so I want to restore my laptop to factory default settings erasing everything and i did because I kept kept getting a blue screen anyways after doing so I tried restarting my computer and the laptop would load and said it was installing windows but then it crashed or something no matter what I did it said it would restart after it fixed the error but I the messages just kept popping up So my friend said just install another win7 disk because you got a product key under neath your laptop which then he gave me a disk but it was win7 ultimate and I installed without knowing but I have win7 home premium so the product key didn't match now what I want to know how do I go about fixing it 1. can I still restore my laptop to factory default settings even though I accidentally installed ultimate and still have the factories original win7 home prem 2. Or do I have to re-install home premium 3. And how do I go about restoring my laptop to factory default settings (deleting)without having access to my operating system I heard theirs like a short key at the boot screen something like ALT F? Idk anyways answers appreciated because I had to type this damn thing on a iPhone and it's a *****.