!This program cannot be run in DOS mode.

ive had some problems with some applications , such as yahoo messenger. i try to open it and it opens up a notepad window with: !This program cannot be run in DOS mode. with alot of other different symbols throughout the page. it seems its trying to open it up in notepad? well i had problems with the 180solutions search assistant popup crud. im hoping someone will know how to fix this problem..also i try to download things and they do the same, such as trying to download window washer.....thanks..