About 18 months back, I acquired a Dell Inspiron 17 running Windows 7. I installed then-current versions of FlashPlayer and Firefox, which worked perfectly together for a few months. Then Firefox started hanging up every time when I ran it after powering up the machine. By trial and error, I learned to avoid this by uninstalling and reinstalling FlashPlayer prior to running Firefox each time I power up, or by simply not installing FlashPlayer. I think some setting changed, since they worked perfectly for a while. The problem has persisted through all updates of FlashPlayer and Firefox; I am now running the latest versions of both.
I also run the current versions of FlashPlayer and Firefox on machines running both XP and Windows 8, with no such problem. Any ideas what this apparent Windows 7-specific issue could be?