About exe file

hello
I have downloaded a software from net. then there was a option of open or open with. I click on open with adobe 8.1 version mistakenly. after it all the executable files of notebook are converted to pdf and all the including camera, ms office softwares stops working. now the problem is that when i installed previous version of adobe the systems works properly but with abobe 8 or higher version it stops functioning properly. now what i have to do.