Adobe problems

I have of late been unable to open pdf files on line. I down loaded adobe 7.0.8 and adobe 8.0. 7.0.8 says that its already loaded but when I search files it says there are no such files. I checked add remove programs and it says there are no such files. When I tried to install 8.0 I get a message that says it can not remove the already existing 8.0, yet search and programs add remove says the same thing as with the 7.0.8. I can down load a pdf file and open it, but I don't always have this option.

So what am I doing wrong in terms of removing the old adobes in order to install the new ones, they must be hiding some where but danged if I can find them.

Thanks
Don