OK, so you have a program called document viewer which is trying to open these files by default. Right click on your file, and select the default program it goes with. What happens then?
You could also have some junk left over from an uninstall or deletion of anything that could use an MSI file to install, which well could be anything.
Have you recently made any changes in your system? Adding a new printer, or uninstalling something, or adding new software? Anything that could have installed this viewer or uninstalled and left it behind.
Also, I would recommend a spyware scan to say the least to make sure something isn't lurking behind on purpose. Also check out this kbase article on Microsoft's page