All my drives have disappeared in Win 10

[Smokey7]

I recently built a Win 10 Skylake system. It has a Samsung 950 PCI Express on the M/B and a Samsung 850 Pro as a 2nd drive. I also have a DVD re-writer and a card reader installed in the front panel of the case.
No problems with the install. Everything working, the 950 being the boot drive. 'This PC' shows all the drives - until the other day when I downloaded 3D Mark to check out the speed of the system. It saved the download to 'Drive N' a DVD boot rom that doesn't exist!. On re-boot it opens the non-existent window for Drive N each time and lists the downloaded files, none of which are accessible of course. But worse, 'This PC' can no longer find any drives at all. Neither can 'Disk Management'. Device Manager lists all the drives correctly and says they're all working normally. The 1302 BIOS in my ASUS Z170 Deluxe shows the C and D drives as always.
I'm a bit stuck here as I've never seen this before. Can anyone shed any light on this?
Thanks.

 

[Puffnstuff]

Sounds like you might try using system restore and roll it back to the time just before you downloaded that file.

 

[VirtualLarry]

Curious malware?

 

[Shmee]

Windows corruption?

 

[Smokey7]

I solved the problem by clicking the 'Clear CMOS' button on the M/B when it got to the Windows password screen.
After this it booted ok and all drives reappeared.
Strange.

 

[LTC8K6]

I solved the problem by clicking the 'Clear CMOS' button on the M/B when it got to the Windows password screen.
After this it booted ok and all drives reappeared.
Strange.

You are brave...

 

[Puffnstuff]

Glad to hear that you were able to resolve your issue.