Hello,
I confirm that there is an incompatibility between Windows 10 Pro - 64bits - and this hardware combination (i.e. motherboard Intel DG31PR + E8400 CPU) : computer indefinitely reboots during startup (a few seconds after displaying the Windows logo).
Even booting from the genuine Windows 10 Pro 64 bits setup (from a USB key or DVD) with no HDD plugged doesn't work : computer reboots in loop.
For a work-around solution, you can either :
- use Windows 10 in 32bits version (instead of 64bits) : I tested that and I can confirm it works
or
- replace this old quirky and crappy motherboard with a better one : I also tested that THIS particular E8400 CPU that I have in my hands works successfully with same version of Windows 10 Pro 64bits on another motherboard (HP computer)
or
- replace CPU and use another CPU model : I tested that DG31PR works successfully on Windows 10 Pro 64 bits with a Core 2 Duo E4600. However, the E8600 has the same compatibility problem on this motherboard than the E8400. So, if you intend to buy another CPU for this motherboard, well, it's kind of Russian roulette here :-)
For sake of details, let me tell you that the BIOS of my DG31PR motherboard is PRG3110H.86A version 0071.2010.0318.1704, and I have 2 memory sticks of 2GB each.
Maybe another BIOS version and/or another memory combination could also be a solution ?
Good luck !