Restoring to a previous date is useless. I wish Microsoft would take it out of Windows. You cant install just Windows Explorer. But what I would do is CLEAN INSTALL WINDOWS!!! Its the only guarenteed way of fixing this. Not to include if you have had driver issues, there is no telling what else is messed up. So get all your drivers from your manufacture's website and get that DVD out.
I would investigate a little bit before clean installing windows. Look in your Event Viewer and see if you can find the root to the problem - perhaps you just need to get a clean explorer.exe from the windows dvd, who knows?
Well if that is messed up what else is? I mean how do you know some core security file hasnt been corrupted. I would waist my time, its going to take you at least 2-3 hours to look through everything and find out the problem, not to include actually fixing it... I can install Windows, install drivers, and run updates in no more than 4 hours. And at that point I know its fixed.