By running mIRC as a portable application you have told it to store all settings and files in the mIRC executable folder.

By design, mIRC checks to see whether the mIRC executable folder contains settings and files and if it does, mIRC automatically runs in portable mode and uses them.

You cannot run mIRC in both portable and non-portable mode from the same executable folder.

If you want to go back to non-portable mode, open the folder where the mIRC executable is stored and delete the mirc.ini and any other extra files and folders.