Please Help with Database Permissions

I am trying to write to a database file that I have set up no my IIS but I am running into alot of trouble. I can read from the database file just fine but trying to write to it is a no go. I am trying to use the "Checking and Setting up the Correct Permissions on the IIS Server" FAQ from this site but I am on XP pro and the steps aren't even close. For example when it says

6. Next the 'Select Users or Groups' dialog box will open, highlight 'IUSR_MyComputer' account from the list by clicking on it. Where 'MyComputer' is this will be the name of your computer. 'IUSER' is the Internet Guest Account setup by default when IIS is installed on the system.

I do not even see the IUSR_MyComputer option there, all I see is Brett- and then a bunch of random numbers and letters. I do not know if this is a problem with how I installed XP, the server that I am running or what. I really need help on this. Thanks.