REG files open in Notepad instead of merging

This is something someone will know how to fix in about two seconds.
For some reason my H-P Notebook/Vista Home Prem 64 is opening registry scripts in Notepad rather than merging them and changing or adding the new keys to the registry. It is now defaulted to this suddenly for some reason. You know like when I attempt to use one of your tweaks for example. It just opens the script up in Notepad rather than editing the registry when download it to destop, right click the file and click merge.
I called H-P but as I'm certain you are aware, they don't know anything. How do I set it back to merge instead of opening the script in Notrpad? I'm unable to install any tweaks because of this. It just started doing this recently. I even tried a restore.
Thank you for your time and attention to my inquiry.

Thank you all who tried to assist me. For some reason, MACHINE repaired himself. I was doing a lot of house keeping getting files and folders in order moving them to a USB external minu-drive and had several zip files for tweaks in the load so I thought, 'I'll just try one on MACHINE [this is the computers name] and sure enough, I extracted the registry file, hit run, clicked merge, and there was the warning about altering the registry. This is so cool.
I've been interested and/or involved with machines and technology since I was about 2 1/2 years of age and I'm 61 now and the coolest feature of computers is, how they can tell you something is awry and then repair it themselves. I've encountered a lot of machinery in my life as an engineer and hobbiest, as well as seen a lot of amazing technological feats, e.g. props to jets, planes to rockets and space travel, but I have not encountered one other thing that is even compares to the marvel of the computer and the informational highway, the internet.
I live for information and technology and to be able to resource all of this wonderful information from the side of my bed is awesome....

Metrotek said:

Thank you all who tried to assist me. For some reason, MACHINE repaired himself. I was doing a lot of house keeping getting files and folders in order moving them to a USB external minu-drive and had several zip files for tweaks in the load so I thought, 'I'll just try one on MACHINE [this is the computers name] and sure enough, I extracted the registry file, hit run, clicked merge, and there was the warning about altering the registry. This is so cool.
I've been interested and/or involved with machines and technology since I was about 2 1/2 years of age and I'm 61 now and the coolest feature of computers is, how they can tell you something is awry and then repair it themselves. I've encountered a lot of machinery in my life as an engineer and hobbiest, as well as seen a lot of amazing technological feats, e.g. props to jets, planes to rockets and space travel, but I have not encountered one other thing that is even compares to the marvel of the computer and the informational highway, the internet.
I live for information and technology and to be able to resource all of this wonderful information from the side of my bed is awesome....

I am a little bit older than you and yes it is bloody awesome.:)