Hi, You need to do the following in order to install the SQL Server 2005 default instance.
First you need to uninstall the SQL Server 2000 default instance.
Then install the SQL Server 2005 default instance by choosing that as an option during the installation process.
Hope this helps...
Cheers,
Basit Ali Farooq
MCITP Database Administrator
Microsoft Certified Professional Developer (Web Applications)
Microsoft Certified Database Administrator
Microsoft Certified Systems Engineer
Microsoft Certified Systems Administrator
CIW Security Analyst
Cisco Certified Network Associate