explorer.exe does not run or even recognized!! HELP PLEASE!!

I have a blank desktop after the Vista loading screen that just shows the
mouse cursor. I cannot ctrl+alt+del or anything unless I run "repair" off of
the disc. Nothing there fixes my blank desktop problem nor does any F8
startup function when booting up my system. I can only bring up the task
manager through the command prompt from the "repair" disc, but it doesn't
show explorer.exe in the processes. I tried putting explorer.exe as a new
task but this is the message I get: Windows cannot find 'explorer.exe'. Make
sure you typed the name correctly, and then try again. I also tried to put
C:\windows\explorer.exe and I get this message: The ordinal 874 could not be
located in the dynamic link library SHELL32.dll. I then tried regedit.
HKEY_LOCAL_MACHINE\SOFTWARE\MICROSOFT\WindowsNT\Cu rrentVersion\Winlogon.
Changed the shell string which read cmd.exe/kstartcmd.exe and changed it to
explorer.exe, but of course, that didn't fix my problem. So what do I do now?!