It sounds like you have a corrupted copy.. I've ran the Modviewer in everything from a W95 machine to Windows 7.. even under Wine on Linux. It's one of the ones that I use to test Windows installs with.
Here's what I'd do to fix it..
a) Redownload a good copy.
b) Reinstall good copies of all the MS VB dlls (MSVB50 and MSVB60 files in \SYSTEM32)
c) Reinstall MDAC 2.8 on your system
Fire it back up and see where it goes..
And compatibility mode can be found under Properties when you right click on the file.