How old is the son that screwed up your pc? if he is not a teen, then you may be up that famous creek without a paddle. Gateway sold out to Acer some 5 + years ago.
See if you can find a Windows 7.0 Recovery disk online. I found one at eBay.com I have it on standby just in case.a couple years ago I had the same problem with a pc that ran Vista. there was a web site on line that would download the ISO for a recovery disc, and the cost was reasonable. it worked too.