Applications Seem Moved from D: to C:

I have an Applications folder on my D: drive and had installed my most regularly used programs there. Sometime in the past two or three days they seem to have been deleted from that folder (it shows 0 files) and the same programs now seem to be in the Program Files and Program Files 86 on my C: drive. I have updates installed automatically, and when there are updates startup seems very slow. When I double click an icon for these files they can't be found. All the other folders on D: are intact.

I successfully moved one of the programs back to D:\Applications, so I should be able to recover most or all of the files, but don't want to be at risk of it happening again.

I'm using Classic Shell, AVG anti-virus, Win8 firewall, EaseUS ToDo backup and recovery, and MalwareBytes. They seldom give me a problem, but could any of them be the cause? Or does Win 8 sometimes randomly move applications? I've gone back through several weeks of posts without seeing this problem addressed. Help, please.