computer freeze from pdf's

I am completely confused on this one. I have acrobat 7.0 and now my computer freezes the minute I try to open a pdf off internet pages( I open online manufacturer pdf files for information) I tried to install the new version but it wouldn't install because it can't remove the old program, and if I try to remove the 7.0 I get an error message stating something about an incorrect "path" so I can't remove or update to a new program. Any suggestions? Thanks