Set up a gift default set for the event:

1. Open the Event record
2. Select Event, Gift Defaults from the menu bar
3. Click the Binoculars in the Default Set selection
4. Click New and select the appropriate defaults including the fund and campaign
5. Click Save and Close
6. Click OK
7. Click OK again

Now when entering the registrant record, the gift is created using the defaults.

OR

Unmark the 'Automatically create a gift when adding registration fees for an event' checkbox:

1. Open Configuration.
2. Click Business Rules.
3. Highlight 'Event Options.'
4. Under 'When adding registration fees to participants', change the radio button to either 'Prompt to create a gift for registration fees' OR 'Do not automatically create nor prompt to create a gift for registration fees.'
5. Click out of Configuration to save these changes.