See if Windows Explorer, (Explorer.exe), works in Safe Mode, (instructions here). If so, then either some add-on is affecting Explorer, or you have malware.

1] Remove all BHOs and other Add-ons from Internet Explorer.

I know you said Explorer.exe, (Windows Explorer), but since Microsoft integrated IE into its Windows Operating System so closely many years ago, Windows Explorer and IE are often affected by the same things, and bad or corrupt Browser Helper Objects, or other IE Add-ons will often spill over and affect Explorer.

Removing them all may help.

2] If not, your next step is scanning for malware, and I would update your anti-virus and anti-spyware utilities, and scan with them in Safe Mode.

I would also download and install MalwareBytes AntiMalware, (MBAM), from http://malwarebytes.org/, open it, update it, then close it down and after you have run full scans with the other utilities in Safe Mode, run a full scan with MBAM as well.

Mark