Greetings wise wizards of EE:
I'm helping a friend with a Dell Windows 7 Pro desktop, that has a very serious issue. According to him, he was working with Avast Antivirus, and while "tinkering", he somehow he managed to set Mozilla Firefox as the default program for ALL executable program files. In other words, when he attempts to open ANY program, including Windows utilities such as System Restore, Mozilla Firefox opens instead. All of the icons on his desktop are displayed with the Firefox log.
The Windows File Explorer does open normally, as well as the Control Panel, but nothing else. He is able to surf normally, but he cannot open any other program. I have encountered this problem before on another machine, though it was Internet Explorer rather than Firefox as the default executable program, and I solved it then by via a reformat & reconstruct the hard drive, but unfortunately I do not have that option here, as he is using some older web design programs, and has lost the installation disks. I have to attempt to restore his machine back to a useful state with all of his current applications intact.
I Googled this dilemma, and it was suggested that a registry modification would do the trick, but the registry editor will not open with the command "regedit".
I would be grateful for any help in this regard.
Many thanks and take care,