Help to work out why a program no longer runs

[simonc8]

There is a bug in Windows notepad.exe which sometimes alters the word-wrapping while you're editing a file. I found several references on the web. To fix this I followed the instructions in

Fix Notepad's CR CR LF bug with a hex editor

and made a copy of notepad and used a hex editor to change just one byte. For several days this ran with no problem but as from yesterday it will no longer run. When I double click on the icon nothing happens, and no window opens. The original unedited notepad opens as normal.

Things that might have changed: windows updates installed - these were mostly for Office 2010 but there was one for 2018-06 Security Monthly Quality Rollup; a full system scan by MalwareBytes, but there doesn't seem to be anything in the scan log to suggest it found a threat.

I would be grateful if someone could suggest things to check that might be stopping this application from running. Grateful for assistance.

 

[mrjimphelps]

I think you messed up Notepad.exe by doing this. Either that, or maybe your antivirus product has detected a change in notepad.exe and is blocking it from running as a suspect program.

You need to run the original unedited Notepad.exe program.

 

[simonc8]

It worked perfectly well for a few days, so it wasn't the file editing that messed up the program.

I'm running Microsoft Security Essentials as my antivirus program, it's showing empty lists for Quarantined items and All detected items.