Digital signature on Delphi application

Hello

I have an application written in Delphi version 5.  When I try to run it on a machine running Windows XP service Pack 2, I get the Windows XP security dialogue telling me that the program is not digitally signed.  I can bypass this, and run the program okay but it is an application that should run a Windows startup without intervention from the user, so I need to be able to get it to run without presenting this dialog box.

Is there a) a way to tell Windows to allow this program to run based on its executable name or b) a way to digitally sign a Delphi application (preferably that doesn't cost any money ;-)

Thanks in advance