Fresh Install Windows 7 SP1, slow internet connection speed - HELP?

I recently built a new rig. I installed Windows 10 on the M.2 SSD, and installed Windows 7 on a separate SSD. Install went fine, installed all the board drivers and activated this copy of Win7.

The trouble: As soon as I try to download a file, the internet connection speed drops to nothing. I can browse the internet just fine. At first, I thought it was a problem with the Intel network adapter, so I purchased a USB wireless adapter, installed it, and, the problem persists.

I tried running speedtest, and the speed starts out fine, right where it should be, but within 15 seconds or so, it drops to nothing.

Literally, ANY file I try to download starts downloading fine, and then nothing.

I've turned off Windows firewall. I've tried running in safe mode with networking. I've uninstalled my virus protection all together.

I'm at a complete loss....any suggestions would be appreciated.

EDIT: Everything works fine on Windows 10, btw....forgot to add that.

Trying to download anything just stops. Oddly enough, though, I can still bring up webpages and browse around just fine, even while the download shows at 0. Got a file right now that's stuck....it's gonna time out soon.

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