See this is confusing which is why I made the thread. I never uninstalled Flash 9, because I didn't know I had to. I never uninstall anything else before installing anything, apt does it for me, like I didn' have to uninstall firefox 2 before firefox 3.
I tried to install flash ten like that website said by downloading it, and I also tried adding the hardy-backports repository and running apt-get install flashplugin-nonfree, but still firefox said it was shockwave flash 9. So I went to that adobe site, and now firefox about: plugins says flash 10. But my friend did the same thing and HIS firefox still says flash 9 even after the adobe site.
The computer in question doesn't have an nvidia chipset as far as I know, it's an Acer Aspire One netbook, and I don't know what kind of video card it has.
This is all very complicated.