Unable to manually open/explore the ipod in "my computer".?

Usually if you want to use the ipod as an external harddrive, you can just go to my computer then click on ipod, and inside you have photos, notes, and calendar. But recently when you go to my computer and click on the ipod it doesn't open, but instead gives you an option that says "open with". This option gives you the most useless programs to open the ipod such as mozilla, word document, notepad, adobe etc.... This only happens on one of my computer (which i need most) but not on the others. Thanks in advance