Since you have mentioned that its a .reg file that you are trying to merge, which gives you a notepad, It seems that it's a file association error. (getting a box that says 'Open With' whenever you try to open something). And I'm assuming you are no longer receiving any popups from the Win 7.
Try this following link. Check whether it helps.
the link is an executable download for fixing exe file association errors mainly designed for XP Operating Systems, but it works for Vista and Windows 7 as well. Just give it a try.
Win 7 Home Security 2012 is definitely a malware infection. I also have McAfee on my machine and it did not stop it from installing on my computer. I think the reason is because it's not a true virus, it's a piece of Malware.
After speaking with McAfee, they told me I should have an issue in the future after I get removed.
I used Malwarebytes in Safe Mode with Networking. After doing some research online, I found step by step instructions on how to remove Win 7 Home Security 2012 at FreeTechSupport.com.
Hopefully this helps as it helped me. I'll continue to keep McAfee because it works well for me, I just need to keep it updated, you should do the same.
XP Internet Security 2012 / XP Security Center 2012 / XP Antispyware 2012 / XP Antivirus 2012 / XP Security 2012 / XP Home Security 2012 all these are same spayware.
If you are trying to remove this spyware, there are full instructions on how to do that manually at the link :
There is a possibility that you will not be able to open any exe file after the removal of virus
I will provide you one registry key. Download and run it. It will fix the issue with that open with issue.
To fix that one try