List all the clients duplicates.

try this command, it should return all the policy names for the specific client.

bppllist -byclient <clientname> -M <master server name>  -l | grep ^CLASS | awk '{print$2}'

you can keep this in for loop to run it for multiple clients..

If you have a list of client names, you could loop through them in a script using this command:

UNIX:

/usr/openv/netbackup/bin/admincmd/bppllist -byclient <client_name> -U 

Windows: 

<Installpath>\VERITAS\netbackup\bin\admincmd\bppllist -byclient <client_name> -U 

PS:
It is a lot easier to assist if you mention/select the OS on your NBU master server.
It cannot be Windows 7....

Your command doesn't work. I go to the install path, then, it tells me, awk is not recognized as an internal command.

But, with this command, I must do it with each client, or is it possible to say, create a list with all the duplicates ?

This is why it is important to mention the OS. 
awk is a Unix/Linux command.

It is not possible to create a list with duplicates - you need to manually go through each client.

Try the GUI as per Andy's suggestion.

Sorry, I'm on windows 7.

But, with the export of the summary of all policies, then with excel, with a filter, I got all the duplicates.

Thanks a lot.

Such a shame you're not running on *NIX!

The following will list the policies for clients that are in more than one policy:

for CLIENT in `bppllist -allpolicies -U | grep HW | awk '{print $4}' | sort | uniq -d`
do
echo "Client: $CLIENT"
bppllist -allpolicies -byclient $CLIENT -U | grep "Policy Name"
echo
done

Hope there's an upgrade path in progress.  No longer supported by Microsoft which means application vendors (like Symantec) aren't going to support it either.