Browser won't remain as default

I really don't understand this fixation with Delta (search toolbar etc)

Step 1:. This was the first thing that I did. There are no extraneous toolbars, Delta other otherwise, to be found under control panel/programs and features. What I'd previously found i.e. bing bar, AVG search, delta, AVG etc I'd removed as unwanted. I've further double checked that there are no leftover folder/files to be found under c:/program files or c:/program files (x86).
Step 2: Adwcleaner has been run (3 times). You have seen the reports
Step 3: IE is the only browser installed. I'd previously run JRT (one of the programs I use and in my utilities folder) This was clean.
Step 4: Malwarebytes has been run and is run regularly as I have it installed. You've seen the report. This is clean.
Step 5: HitmanPro not one of my regular malware programs but this has been run and as I expected it was clear.
Step 6: (not on your list) Spybot Search and Destroy run and clean bill of health given; no issues detected.
Step7; (not on your list) HijackThis ran. You have seen the report. Nothing appears suspicious and certainly no indication of 'Delta'

I'm running AVG free addition. Same as that used on XP partition and Windows 8.1 disc (multi-boot configuration). I'm having no problem with these. I'm coming to conclusion that I'll have to do a repair install of Windows 7 unless someone knows whereabouts in the registry i.e. what key pertains to this IE feature. I'm sure an object key is corrupt.

There are quite a few registry keys that get set when you pick a default browser. I could not figure out a way to tell the OS that IE was not the default browser if no other browser was installed... so, I installed Chrome. This is what I captured when I started IE and told it to be the default browser again:



The Process Monitor results are filtered on operations that contain the letters regset. As you can see, that includes setting security on some of the keys and (for some reason) apps set the same info to the same key multiple times. So, the 69 entries that you see does not mean that there are 69 different keys being set. But there are still quite a few to look thru.

The one that I'm showing in regedit does not seem to matter to IE - in other words, I can change that key to Chrome, then start IE and IE does not ask to be the default browser. I'm not sure which key(s) IE looks at before asking to be the default browser and a quick Google search did not help.

You could install Chrome and see if it will stay as the default browser - then set IE back as the default browser ans see if it stays. You should always have more than one browser installed in case one gets hosed.

Many thanks to all who have responded to my request for help. This is much appreciated. In the end I decided to perform a repair install of Windows 7.

Interesting in that the contents of the Compatibility report indicated

"The following issues are preventing Windows from upgrading. Cancel the upgrade, complete each task, and then restart the upgrade to continue.

• Windows needs to be restarted so necessary changes to system files can be made before continuing. "

Didn't realise I was upgrading as opposed to repairing. Obviously I had system file corruption . However on completion of repair/upgrade and subsequent update, IE now set as default status and remains as default