I'm on Windows XP (service pack 3) and was updating Flash player when my computer suddenly shut off because I'd accidentally stepped the power cable, causing it to be unplugged. I turned my computer back on and attempted the install again, but now every time I try to install Flash, Adobe Installation Helper "encounters a problem and needs to close." This happens immediately after I double-click the installation file. I've tried downloading another copy of the installer and restarting my computer normally.
Should I uninstall Flash and reinstall? I'm worried that the installer might not work, and I'll be left without any version of Flash instead of a now-outdated one.
Since the machine shut down unexpectedly, I would check for and repair any errors on the disk before installing or removing stuff. This may save you some headaches.
After that, a clean install is probably the way to go. I would just run the uninstaller. If the install fails, then do it again with the optional steps of manually deleting the stuff that's listed.
Firefox and other NPAPI browsers: