No you can't read the registry, but I've seen a js flash detection script 
here
http://www.xs4all.nl/~ppk/js/index.html?version5.html

hth
Phil
>-----------------------------------------------
> Just was wondering if this was possible. I am trying to see if a 
p> articular (flash6) plugin is installed by using it's registry ID. 

> I want to do it this way because using the code I obtained from the 
flash 
d> evelopers kit works fine 6 of the 7 computers I test on, but on this 
one 
c> omputer (windows2000 laptop) with flash 6 installed it displays 
the "not 
c> orrect flash player version...".

> Anyway, any help or info on this matter would be greatly appreciated

> Thanks