I don't use AutoCAD but I can think of two possible scenarios:

1) Someone messed with your PC while you were on vacation. If so, try System
Restore to a time prior to your vacation.

2) If you are on a network, perhaps the administrators applied a Group
Policy that made the changes. If so, have a chat with your IT department to
work out a fix. You could try a System Restore but if it really was a Group
Policy change it will revert back to the policy settings.

Tim


"Tyree" wrote:
[color=blue]
> I use AutoCAD software daily at work. Autodesk just recently updated AutoCAD
> to work with Vista. Version 2007 worked with Vista, but not well. For one
> thing a .dwg file did not open in AutoCAD by double-clicking it. You also
> couldn't add AutoCAD to the Default Programs list.
> Great thing was, when I installed AutoCAD 2008, that was fixed as well as
> all the other issues that 2007 had with Vista.
> I was on vacation last week and arriving back at work today, I have found
> that AutoCAD is no longer the default for .dwg files. Worse yet, the Default
> Programs window will not allow me to add the acad.exe file to the list of
> applications to choose from. I click Browse, select the acad.exe file, click
> Open, it goes back to the Default Programs window and NOTHING happens. No
> error, nothing.
> WHAT - THE - HECK???
>
> So, question 1, why did it change the default program?
>
> Question 2, why can't I add AutoCAD to the list?
>
> Thanks,
> Matt Tyree[/color]