Under Windows 2000, viewing or modifying security on the Registry involved the use of a separate, somewhat clunkier Registry Editor interface invoked with regedt32.exe. Fortunately, Windows XP does away with the regedt32 interface and integrates access control into regedit.exe.
Registry security uses an access control interface similar to what you would see when managing NTFS or network share security settings.
It's quite rare that you would need to adjust permissions on registry keys. About the only time I've had to do this is when an application program's installer adds registry keys with read/write permission granted only to administrator. If you want to run the application from normal user accounts, you have to adjust ...