Open With Dialog Box Always Open

Whenever I try to run programs such as Internet Explorer or Microsoft Word I get a OPEN WITH dialog box asking me to choose which of the recommended programs I want to use. Currently they are Internet Explorer or Microsoft Word. When I click on Internet Explorer, IE momentarily open then closes and another dialog box open. asking me if I want to run c:programs filesInternet Exploreriexplore.exe. When I click on RUN another dialog box open asking me if I want to run Windows Vista SE Build. If I click on RUN I return to the OPEN WITH dialog box and starts the cycle over again. When I tried to run PROGRAM UPDATES in the CONTROL PANEL, I got a message about not being able to find RUNDLL32.EXE. Thinking I had a corrupted file, I copied a good RUNDLL32.EXE from my primary machine. No change after copying the file.I've run Norton AV and found no viruses. Interesting in that running Norton's did not initiate the OPEN WITH dialog box.