I rand into this issue with windows 8.1 and my Q8400 on an Intel DP35DP motherboard
I had one of those motherboards a few years back...bought it with a Core 2 Quad Q6600, which I think would've been sometime in 2008. After maybe a couple of years or so, the motherboard started acting iffy. I kept the processor, but replaced the motherboard. It's been running on a Gigabyte EP43-UD3L ever since. It currently dual-boots Gentoo Linux and Windows 7 from an SSD, and I threw an old hard drive in it recently to try out Windows 10. It runs like a champ...probably about the same speed as Windows 7, when I had it on a hard drive. I'll most likely nuke Windows 7 off of the SSD and move Windows 10 into its place.
tl;dr: Your problem with Windows 10 most likely isn't with your processor. Try upgrading the motherboard's BIOS. If that doesn't fix it, you're most likely looking at replacing the motherboard. You can probably find something cheap on eBay that'll work. The EP43-UD3L seems decent enough; I've even had Mac OS X running on mine at one time (at least up through Snow Leopard).