This functions (somewhat) like the rcx.d scripts that run upon startup on a Unix machine. Click “Start > Run…”. Type “regedit” in the text box to open the Registry Editor.
HKEY_LOCAL_MACHINE > Software > Microsoft > Windows > CurrentVersion > Run
You should see a list of applications that run on startup in the right panel. Right-click, and choose “New > String Value”. Name it anything you want, then double-click this new entry and enter in the “Value Data” field:
regedit /s D:\path\to\registry\file.reg
You will need to change the path, of course. The /s basically indicates a silent import of the specified registry file.