In a word, Yes.
Access 2003 .adp files work without problems with databases previously
created on MSDE 2000 upgraded to SQL Server 2005.
You can't design tables, procedures etc in Access 2003, but you can do all
that (much as you did with Access2003 / MSDE 2000) in SQL Server Management
Studio Express.
Make sure you install SQL Server 2005 with Advanced services!