try running explorer.exe in the run line.
Okay now, I have fixed my explorer.exe problem, but only by doing a system restore on Windows Vista.
It seems that after installing a DVD creating/burning program, my system became unstable and decided to not completely load my desktop, task bar, icons, etc.
If you have recently installed a new software program (any kind), try uninstalling it 1st, then restart your computer and see if everything will load up correctly.
If that doesn't work try restoring your computer to a recent restore point when you know that your computer was functioning properly. (Before whatever installation caused the problem to happen)
I restored mine to a time that was before the menacing software installation. I was hoping I could find a fix for this whole explorer.exe issue without having to do a restore, but I was unsuccessful.