Open or save in IE8

:mad:I have an app written in vb6 which downloads some files to users machines and then allows them to use the app on the web.

I created an update last week and it would download fine on my machine (XP with SP3) which now has IE8. The original software was downloaded via IE7.

However on machines which have IE8 that never had the software it pops up the message box Do you want to save or find a program online to open it.
frmxxx.vbd unknown file type

I can not find any help that solves this issue. I have checked and the security settings are set to medium - low, cab file is signed, allow unsigned active x enabled.