Find a friend/neighbor/et cetera with a retail Windows Vista DVD, insert it, restart your computer, and press any key to boot from CD/DVD when prompted. (You may have to edit your BIOS settings to set your optical drive as your primary boot device.) Once the Windows Vista installer launches, proceed through the keyboard/language selection and, instead of clicking Install Now, choose "Repair my Computer" from the bottom left corner.

From there you can try two things:
1.) Running System Restore, reverting to a time prior to when the problems began.
2.) Using the command line to repair Windows file corruption.

If neither work, and you have no other admin accounts (and cannot create them now), you may be better off backing up your personal files and reinstalling from the Dell DVD given the unavailability of the command prompt and various admin controls.


P.S. PSTScan.exe is only for repairing Outlook files.
P.P.S. You will normally see multiple instances of Rundll32, one for SYSTEM and one for every user currently logged in.