Here we go again...
After running Firefox_Portable_1.5.0.7_en-us.exe inside the folder 'D:\FP' and then running FirefoxPortable.exe inside the folder 'D:\FP\FirefoxPortable' I recieve the infamous "Another instance of Firefox is already running. Please close other instances of Firefox before launching Firefox Portable." error.
Needless to say, I did a search for 'another instance' in the Forum and remain at a loss as to how to correct this.
https://portableapps.com/search/node/%22another+instance%22
Some of the forum posts are silly like "don't change the name from Portablefirefox.exe to firefox.exe". Others downright stupid "Just restart the computer, it could be a extension running?". This one is almost criminal "put the .ini file in the same folder as the PortableFirefox.exe"
How can Firefox Portable NOT run when other things are running. Half of all the reasons to use Firefox Portable are to run multiple instances. This issue has been around since December 2005 at least and still pops up today.