So since I upgraded from win2000 to XP, when I open an attachment directly from outlook express I get -
"Not a valid win32 application." message. I can download the file to the hard drive THEN open it, but I like to open sometimes without actually saving to the hard drive.

I get the SAME message when I try to open a file directly from Winzip. Again. I have to UNZIP and save to the computer, where before I could open directly from Winzip.

Looks like your file associations could be messed up. Try THIS first and report back.

Well, I did it and I got a quick black MS DOS screen that disappeared then nothing happened. I tried to open the attachment I got today and it still gave me the same error message.
c:\documents and settings\Maryann\Local Settings\Temporary Internet Files\Content.ie5\aw060704336e01c.ai is not a valid win32 application

Hi, try this...open Outlook Express go to tools>options> then click security tab and uncheck the box that says "Do not allow attachments to be saved or opened that could potentially be a virus." then click apply and ok out of it.

It didn't work.