The brain dump of bogge.
Solution
Probably, it is a conflict between a Merge Module and a Component. Remove the Component then Merge Module is better to use.
If Component name is comctl32.ocx then you should use the merge module: COMCTL32, so delete the comctl32.ocx Component.
Solution
The table is most likely missing.
For example, if there is “Internal Error 2728. Component” then table “Component” is missing, this can be fixed by putting install dir and recompile package.
Solution
RemoveExistingProducts is not in the right place. Move it between InstallValidate and InstallInitialize.
Solution
You do not have enough rights to create / change this value in the registry.
In some cases the value is in the wrong format. As an example, you may have a DWORD reg value with the value 0×300, but it should be written in decimal form, 768, in order to work.