For a build process template, we can add/remove/edit the argument list of it and use it as variables within the build/work-flow steps. I reading the nice guide
Use the below script to delete the registed build process template in Database:
use Tfs_YourTeamCollectionName;
delete from tbl_BuildProcessTemplate where ProcessTemplateID = 'Your ProcessTemplateID';
Create new build definition again.
The database name is your TFS team collection name e.g. Tfs_YourTeamCollection in the backend SQL Server of your TFS server. I'm using TFS 2012.
Hope it helps!