Hi there TheStagGamer,
That is really unpleasant.
My suggestion would be to back up the data stored on your E: drive. Is the drive under warranty? There are a couple of weak sectors on the drive.
After that, my suggestion would be to reformat the drive and re-test it. In case there is no chance in the SMART data, you can even write zeros on the drive(process that fills in 0 value in each sector) and retest. You can do so with WD's Data Lifeguard Diagnostic tool. I will not hurt to run both its short and extended tests:
http://products.wdc.com/support/kb.ashx?id=a9AP65
As for the 100% disk usage, you can take your problematic drive out of the system and see if the issue persists. In case it does, then this is most probably caused by some Windows services. There are multiple threads on that with different causes and solutions to that issue. It may be a good idea to do some research on that.
A couple of threads:
https://www.reddit.com/r/techsupport/comments/3h4wjg/windows_10_high_disk_usage_100_ive_seen_a_thread/
http://www.tomshardware.co.uk/forum/id-2813275/disk-usage-100.html
Let me know how this goes,
D_Know_WD