Problem with windows explorer and installing software

My Widows explorer periodically slows to a halt requiring me to use ctrl-alt-delete to turn it off, after which it immediately becomes normal again.

Also, when I try to install a new device (camera, etc.), my computer says that I can't because something else is in the process of installing and nothing else can be installed while the other thing is installing. Problem is, nothing is being installed to begin with.

No spyware, adware, virus problems (went through that in February). Normal HJT log. Any clues to this last computer mystery on my -puter?