You Can download a win 7 sp164 from
Here These ISO's are quite legal and you will just need make sure you download the version your computer came with. See this
Thread for how to if you need help clean installing
Its really no issue for win 7 sp1 64, you just have to make sure you create a UEIF GPT install media and insure that you boot it up UEIF. Of course the USB thumb drive is the very fastest way to do this, Its been a while but I think the last time I installed win 7 it took all of about 10 minutes. 18 months ago, you should have gotten a win 8 pro $14.95 upgrade, you might want to consider this a good time to Clean install that as 8.1 pro 64?
G752VY-DH72 Win 10 Pro
512 GB M.2 Samsung 960 Pro
1 TB Samsung 850 pro 2.5 format
980m GTX 4 GB
32GB DDR 4 Standard RAM
Z97 PRO WiFi I7 4790K
Windows 10 Pro
Z97 -A
Windows 10 Pro