This is the Task Manager when it happens: 100% disk usage, 0 ms response time, but 0Kb/s in and out and it happens for over 35 seconds. The whole system just stops for just about everything. Programs that are completely loaded and don't access disk are fine. (i.e Task Manager) Not so good when gaming though.
Someone else must be seeing this I'm hoping and maybe have a solution. I've read of some others seeing it but also the same issues in 8.1 so maybe I was lucky not to get it then.
Update 29/12/15 I had another look at this over the Christmas break and may have made some progress. I downloaded the driver for the AHCI for the nForce controller on this motherboard and it seems to be better (touch wood)
I wouldn't install the whole package of drivers but I downloaded the Vista 64 bit drivers (Windows 7 64 bit showed no downloads for some reason) and updated from device manager the storage controller and in a few hours testing no more 100% active 30 second lock ups. Far from conclusive but hopeful.
So yes it's an old board but there's bound to be others with the same or similar issue. The nForce storage driver in windows 10 looks a bit broken.