At the end of the SQL Server 2005 SP2 installation you may be prompted to launch the SQL Provisioning Tool. This utility makes members of the local administrators group SQL Server sysadmins - which is cool, especially if your instance security is Windows Authentication only.
If anything "bad" happens during the provisioning process, the utility simply shuts down.
By "bad" I mean things like the tool attempting to access a service you shut down. Note: you may have shut down this service because you were prompted the file was locked during an earlier step in the Service Pack installation.
When you search for the Provisioning Tool in the Start Folders you will note it isn't there.
You can find it with diligent searching (or by reading this blog): It defaults to [Installation Drive]\Microsoft SQL Server\90\Shared\SqlProv.exe. On my machine I installed SQL Server on the C:\ drive so my path to SQLProv is "C:\Program Files\Microsoft SQL Server\90\Shared\SqlProv.exe".
Re-executing the tool doesn't seem to cause any negative impact, but I haven't conducted rigorous testing.