If Flash has 'disappeared' from your PC:
First, go to Add/Remove programs and uninstall 'Adobe Flash Plug-in'
Then get the download from here:
http://get.adobe.com/flashplayer/
If you have problems with Flash Player 10, try downloading Flash Player 9 instead:
http://oldapps.com/download.php?oldappsid=flas hplayer9r115_win.exe
NB: Remember that downloading a set-up file won't install anything onto your PC. You have to save the file to a convenient location and then double-click on its icon to start the installation process.
Chris