I’ve been having issues with 100% drive activity on Windows 8.1 and had a chance to look at it today.
I ran chkdsk /r on my SSD but this didn’t help. I opened Performance Monitor to have a look at things and had a few tabs in my browser open with troubleshooting tips. When I noticed that my sata DVD drive was not being detected by the OS I opted to open up the case.
I unplugged all of my sata cables and plugged them back in (and checked the power connections for good measure).
After that everything has been working fine – sometimes it is the simple things that make all the difference!