I had massive problems installing Reader 8.xxxx because of problems on my
laptop. There are some fixes available that clean things up nicely... But you
have to search on the Adobe website for help there.
You're lucky, for me, I couldn't get past half-way when installing the
reader upgrade. I think it comes down to some "dandruff" being left behind
from past installs. It's pretty insidious how many locations things end up in
during a so-called simple install.
In general, I've found the Adobe site helpfull in fixing these issues (ran
into it with flash player install from them as well.) Sorry, I don't have the
links anymore.
Matt