Database "msdb" cannot be opened due to inaccessible files or insufficient memory or disk space.

I am using SS2005 on XP and things have been good. Today I installed
"Microsoft SQL Server 2000 DTS Designer Components" (I can't think of
what else could have caused the problem), and now in SS2005 Management
Studio I am getting this error message when I try to connect to the
server on my machine:

Database 'msdb' cannot be opened due to inaccessible files or
insufficient memory or disk space.

Any ideas??? Thanks!

-John