Yes, you can install SQL 2005 Express on the same computer.

Be sure that when you are asked if you are upgrading or installing a new
instance, that you select 'new named instance'.

I don't know what (or how) Backup Exec is using MSDE, but I doubt that it
would notice the difference if you did an upgrade. HOWEVER, such an upgrade
would need to be thoroughly tested. Perhaps if you contacted VERITAS with
the question of their product working with an upgrade of MSDE to SQL 2005
Express.

--
Arnie Rowland, Ph.D.
Westwood Consulting, Inc

Most good judgment comes from experience.
Most experience comes from bad judgment.
- Anonymous


"Ernie Kuo" <ErnieKuo@discussions.microsoft.com> wrote in message
news:EF7D6D6A-ED15-4D96-A576-D3D7BA687037@microsoft.com...
> Hi there,
>
> I have a server running Veritas Backup Exec which is using MSDE 2000, but
> now we want to run ACT! 2007, preferably on the server, which need SQL
> 2005
> Express Edition.
>
> So......can I install SQL 2005 Express Edition and have it running at the
> same time as MSDE 2000 OR is SQL 2005 similar enough to 2000 that
> something
> like Backup Exec won't notice or care?
>
> Thanks in advance.
>