error message

I finally installed MSDE and have the icon in my tray at the bottom of the screen.
When I try to connect to a database using the wizard in the web matrix program I get this message:
Unable to connect
SQL Server does not exist of access denied
Connection Open (Connect ())
What might be wrong??
Thanks for your help I'll get it soon (I hope)
Del Dobbswell, are you specifying the correct instance name? username? password?|||see this

http://support.microsoft.com/?kbid=328306