Active Registry Monitor (ARM) is an utility designed for analysing the changes made to Windows Registry - by making the ;snapshots; of it and keeping them in the browsable database.
You can compare any two snapshots and get the list of keys/data which are new, deleted or just changed. ARM can do comparing not only in the entire Regisrty, but also in any key of the Registry.
It is also possible to exclude any keys of the Registry from compare results. Moreover, you can create undo/redo files (for example, to rollback the changes).