it sounds like you have a virus. there is a virus that destroys your system volume so you get similar problems. you get this virus from porn sites saying you need the latest flash, download now, when you know you already have the flash installed.
there is different flash for IE compared to firefox.
to see iif you need to reformat because of the virus
right click my computer icon >manage >system >disk management.
In the RHS pane if you cannot see C drive, then you need to format and clean install windows.
if c drive is there, then try this
Flash problems
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In XP, go to add remove programs and uninstall macromedia shockwave and also uninstall adobe flash, and adobe shockwave.
Using Explorer, go to c: windows/system32/macromed and find the uninstall active x file in one of the folders, and run it.
Then delete the contents of macromed folder. If a particular file will not delete, right click >properties and un-tick the read only attribute. If it still will not delete , boot in safe mode and delete it, them boot normally.
Then google adobe shockwave and install it.
Then google adobe flash and install it. You will have to allow active x to help install which is ok.