There's two versions of Flash, one for IE (ActiveX version) and the Plugin version for other browsers. You need to install the Plugin version.

1.Download the Flash setup file from here:
Adobe Flash - Plugin version.
Save it to your Desktop.

2. Close Firefox using File > Exit
then check the Task Manager > Processes tab to make sure firefox.exe is closed,
{XP: Ctrl+Alt+Del, Vista: Shift+Ctrl+ESC = Processes tab}

3. Then run the Flash setup file from your Desktop.

• On Vista and Windows 7 you may need to run the plugin installer as Administrator by starting the installer via the right-click context menu if you do not get an UAC prompt to ask for permission to continue (i.e nothing seems to happen).
  

See this:
http://vistasupport.mvps.org/run_as_administrator.htm

I'm using win XP. Even uninstall, Close all firefox (portable) and firefox container, then reinstall from adobeflash10.exe, it still not work.

I would like to use tor but tor require portable firefox. I also tried to use Operabrowser (Opera Tor version), but it has the same problem. Problem, maybe, portable cannot regcognize flash player.

Please help.

Now I've found the answer. http://www.torproject.org/torbutton/torbutton-faq.html.en#noflash I can't view videos on YouTube and other Flash-based sites. Why?

YouTube and similar sites require third party browser plugins such as Flash. Plugins operate independently from Firefox and can perform activity on your computer that ruins your anonymity. This includes but is not limited to: completely disregarding proxy settings, querying your local IP address, and storing their own cookies. It is possible to use a LiveCD solution such as or The (Amnesic) Incognito Live System that creates a secure, transparent proxy to protect you from proxy bypass, however issues with local IP address discovery and Flash cookies still remain.

If you are not concerned about being tracked by these sites (and sites that try to unmask you by pretending to be them), and are unconcerned about your local censors potentially noticing you visit them, you can enable plugins by going into the Torbutton Preferences->Security Settings->Dynamic Content tab and unchecking "Disable plugins during Tor usage" box.

If you do this without The (Amnesic) Incognito Live System or appropriate firewall rules, we strongly suggest you at least use NoScript to block plugins. You do not need to use the NoScript per-domain permissions if you check the Apply these restrictions to trusted sites too option under the NoScript Plugins preference tab. In fact, with this setting you can even have NoScript allow Javascript globally, but still block all plugins until you click on their placeholders in a page. We also recommend Better Privacy in this case to help you clear your Flash cookies.

The Tor Browser Bundle does not work with Flash or other plugins by design. If you wish to run these plugins over Tor, you need to install Tor and configure your own instance of Firefox.

I have done everything specified in the answer to my post above. I exited Namoroka, installed Adobe Flash Player 10.1.102.64, and checked Programs and Features ... it is there.

Namoroka/Firefox still does not see it!! Checked the Add-On's too ... not there.

This post was a big help for me. Firefox has a funny habit of not closing even though you've exited. The part about going into Task Manager and verifying Firefox has closed is particularly relevant. Thanks the-edmeister!