In ArmA 2 v1.05 patch they introduced the pbo file association to arma2.exe for some reason. Many people in the community do not like this because community made pbo tools like cpbo.exe stopped working.
oktane provided method to remove the pbo file association.
First you need to open My Computer to go into windows explorer and create file shall we call it Remove_ArmA2_PBO_association.reg
Do this by right mouse clicking on the explorer window, choose New → Text Document. Then give it file name: Remove_ArmA2_PBO_association.reg
Now use your favorite text editor to open this .reg file, then copy paste this code there:
Windows Registry Editor Version 5.00 [-HKEY_CLASSES_ROOT\PBO_auto_file] [-HKEY_LOCAL_MACHINE\SOFTWARE\Classes\PBO_auto_file] [HKEY_CLASSES_ROOT\.pbo] @=- [-HKEY_CLASSES_ROOT\.pbo\AppsTable]
To run the just created registry file is easy. Just double click on the Remove_ArmA2_PBO_association.reg file on windows explorer and choose Yes from the dialog. Done.
If you are running Kegety's CPBO tool to handle your pbos and want to bring back its pbo file association, you need to go into the directly there cpbo.exe is located and double click the cpbo.exe in windows explorer (or desktop short cut what ever you got for it).
Then choose Yes from the dialog to associate cpbo yet again with pbo files.