When .pdf links are clicked, they download, rather than open

[6680abhi]

On one of my computers, when I click a pdf link, rather than opening the file in Adobe Acrobat Reader, it asks me to download the file. On my other computers, however, it opens them.

This occurs in IE 6.

In Firefox, however, PDF files seem not to load; you click the link, and are left with a blank screen, saying "done".

How do I resolve this problem?

I am running XP SP2, And have Adobe Acrobat Reader 7.0 Professional.

Thanks