On Win7 I can take an EXE, right click on it, show properties, and get a tab called Compatibility.
In Vista I don't see the compatibility Tab. How can I set compatibility mode for an EXE in Vista - or can I?
This can be missing if it was an in place upgrade from XP to Vista, seems registry entries for SYSTEMROOT and WINDIR have the wrong string value, the article is not specific where these entries are or how to correct them.
Another reason can be 2 system files are missing from the system32 folder, "wer.dll" and "Faultrep.dll" I am not sure if System File Checker will fix this or not but is best to try this before downloading unknown versions of the files. You can also search your hard drive for these files, there might be backup copies of them in another folder that can be copied to the System32 folder.
If you used Vlite to customize the Vista install disc, see this page
Seems there can be a few reasons it is missing.