Hey Jim,
You probably have some type or "start up" item, (?Virus / Spyware?) or
maybe even a "Browser Add-On", that is effecting Windows Explorer from
running properly.
You may even notice that apon booting to desktop, explorer may seem to
load then flashes off quickly (sometimes)...
-This can most likely be solved by one or more of the following:
1) Disable "3rd Browser Extensions" from your internet options in the
control panel / Advanced tab.
2) Open MSCONFIG from the run line (Start/Run...):
-Disable ALL start-up items on the "Startup" tab.
NOTE: If the above works then you will have to start to turn these startup
items back on to determine which one it may be causing your problem.
3) Run a full system Virus & Spyware scan (OneCare by Microsoft / Ad-Aware
by Lavasoft/ AVG Antivirus by Grisoft/ Trendmicro.com / Windows Anti-Spyware
by Microsoft)
If all else fails... back up your important files and format / clean install.
Hope this was helpfull
JU$T1N