How can I see and change what Program Compatibility Assistant did?

After working fine for months my Comodo Firewall failed to start properly on one bootup. Without giving me the option to say do NOT make any changes--for each of the two dialog boxes, I said just close the program--the PCA popped up saying it had applied a compatibility fix! (In the past on older OS's under similar circumstances, I would simply reboot and things would be OK afterwards WITHOUT having my system changed.)

How do I see what change(s) were made and, hopefully, undo them so I can reboot my system and see if the trouble reoccurs? Thanks.

I'm not sure PCA creates a log. You could just uninstall comodo, disable PCA, then reinstall.

Program Compatibility Assistant - Enable or Disable

Alternatively, you could try a system restore to a point earlier in time before the compat fix was applied.

Thanks. What I did do was locate and edit the registry--after backing it up first.

The registry location is HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AppCompatFlags\Layers

I had something similar happen recently involving the early development version of Firefox aka Trunk/Minefield. My assumption is that either during an install or as a result of a crash, Minefield had a compatibility fix applied to it.

My first indication was despite having the pref in Minefield properly set my one Win7 system refused to show each tab as previews when hovering over the Minefield icon in the Task Bar. (My Firefox 4 showed the previews without issue.) After an exhaustive search of the registry, I located the above location. Having a second Win7 system, I was able to compare the two system and the keys in the Layers location. After removing the Minefield entry from the affected system, the Task Bar preview functionality for Minefield was restored.

Of course, all the precautions apply when in the registry such as always backup before making any changes to the registry.

What I wish for is Micro$oft to have provided a way for we users to see what compatibility fixes have been made and allow us to "undo" those fixes in such situations as I have recently encountered without having to disable PCA because it IS of value for programs that DO need compatibility fixes applied to them. I also wish PCA would not just apply the fix, but offer us the option like Windows does on BSOD's to try, again, without making any compatibility changes. (Or, as I have so frustratedly found out restrict such access to higher versions of the OS, likely just another way to pry more $$$ out of our hands.)

The event log will tell you exactly what changes were made by Application Compatibility -- though I am not sure which event log to view -- I had to create a filter from all of the logs for the time period in which the change was made.