What would make life really easy for installers would be a virtual filesystem driver as to where a subdir in the FAT/NTFS filesystem can be a symlink to the registry.
This way you could extract a zip file into a directory and registry entries would be automatically created.
Removal would also be simple : remove the subdir and registry entries pointed by the symlink would be deleted too.
I know that MS-software also write in MS-specific keys, but this has always been a faulty design I think. The same goes for software which overwrites DLL's in the system directory and not to mention the lack of version control in DLL's

Frank van Gestel