My PDF Files Open in Notepad

hello i have a problem on my vista 64bit computer with the pdf files when i open my pdf files it opens in a notepad file this only happens when i click on the file twice then it opens to notepad
All PDF files were and always are associated with Adobe Reader, but I really don't know why they open in Notepad instead of Adobe Reader!
when I right-clicked on {file}.pdf,in the context menu i see the name read(bolded) when i click on read then it opens pdf files in the normal way as it schould be when i dont use the context menu then it opens in a notepad and all the pdf icon has not change in to a note file icon i can see all my pdf icon as thy schould be looks like so i wander what is wroung here can anyone advice please what i can do to get this working properly again