There are probably many more ways to get a count of your donors.  Here are just a few:
  • If you are looking for just a count, then Profiles > Reports > Profile Affiliation Analysis is a report that will list the number of profiles with each affiliation code.  Since the donor affiliation is added automatically to a profile the first time they have a gift posted, the count next to the Donor affiliation should work.
  • Similarly, if you run an export to word processing and select on the donor affiliation, the count of records exported ( make sure you check the ignore allow mail flag on the mailing tab), will be your count.  As a bonus, if you want to mail to them you now have a file.
  • You can also run the Reports > Profiles > Profile listing and select on the Records group and choose GiftHistory exists and enter Yes in the from and through.  This will list all the profiles.  At the end of the report is a Number of Records count.