Problem with Flash in Firefox Portable on win7 & 8

Hi, I have a very annoying problem with Flash Player in Firefox Portable on windows7 and 8.
I put the files "FlashUtil32_18_0_0_232_Plugin.exe", "NPSWF32_18_0_0_232.dll" and "plugin.vch" in the "FirefoxPortable\App\DefaultData\plugins" folder. I restarted the app and, on my windows XP machine, it worked perfectly!
Then when I used the browser on windows7 and 8 but it didn't work! I tried it on 5 different machines, 4 with different flavors of win7 and at least on my Win8.1 tablet but it's always the same: where the video should be played there is a blank black square!
I tried with different versions of Flash and Firefox, I pasted all the files contained in the C\WINDOWS\system32\Macromed\Flash folder in the Firefox Portable plugin directory but nothing.
When I check the installed plugins in the about:addons tab Flash is there and it's set to always activate!
I noticed, while I was watching for the active processes on the task manager, that the plugin container always crashes and restarts when I try to watch a video so I disabled the plugin container feature but the problem remains.
I installed locally on my win8.1 tablet the flash player and it works fine with Firefox Portable.
I really can't understand what's wrong, especially because everything works great on XP!
Is someone able to help me please?

P.s.: excuse me for my bad English.