FYI: Explorer.exe is not Internet explorer it is Windows Explorer which also runs the desktop (unless separated using special settings to run as two program iterations).
I would recommend running a system repair (from the W7 DVD or repair DVD) to see if that finds and fixes any corrupt system files.
Next suspected culprit would be something that loads on boot-up. A possible cause is a virus or it could even be your actual anti-virus software ... so what AV do you use and have you run a full system scan lately? You could also try a secondary passive scanner (one you have to run manually) as a back-up to whatever active AV you are running. A good example is Malwarebytes; links for which can be found in our
Freeware DB.