"Class Not Registered" Error Message: Huh?



I run Vista Home Premium on my HP laptop. When I try to open the recycle bin, or if I try to open items on the list that pops up when the start button is clicked (Computer, music, network, games...) I get an
error message window with a large red X and it says "CLASS NOT REGISTERED". What's going on, and how do I fix this?
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