Hi,
I only had to type:
c:\>ppm install dbi
and it works fine for me.

You can do
c:\>ppm
and then type in the console
search dbi
PPM should tell you if there is any package like 'DBI' in your repository
The repository is the location in which activeperl looks for modules
You can view/set your repository with 'set' command on ppm interface.
For example
c:\>ppm set
In my activeperl (build 626) is
ActiveState Package Repository: http://ppm.ActiveState.com/cgibin/PPM/ppmserver.pl?urn:/PPMServer
If you aren't able to install the module (It should happen) you can "force" PPM to search in one place using the ppm "install" command with "location"
This is the syntax for the ppm "install" command,
PPM> help install
install --location=location package1 ... packageN
So you can type
install --location=http://www.activestate/packages dbi
install --location=http://www.activestate/ppmpackages/5.6 dbi
and so on
Hope this helps
Hopes