When configuring a SharePoint 2007 farm through the Central Administration, you should always use domain accounts for you services, to avoid errors or strange behaviors. But what happens when you just need to configure services in a stand alone enviroment?
For web site's application pools identities you should use the default Network Service account, but when it comes to configure SharePoint's 2007 Services, the easiest way is to create a local administrator account and use it to run all your services. 

Almost every Central Administration's page uses a people picker to avoid errors, but sometimes you will just see a blank textbox which asks you to input the credentials for running determined service.  This is the place when sometimes strange errors starts...

Here's an example:
during a Shared Services configuration in a stand alone enviroment, I was configuring the Index Service and when I was asked for credentials, I have simply insered the new local admin account I've created.
SharePoint 2007 didn't like it and reported this error:  An unhandled execption occurred in the user interface: OSearch.

WTF?
Why they didn't provide any information about the error in that page? 
Anyway, you can solve the problem by preceding your admin account name with your server name: YOURSERVERNAME\YourAdminAccount.

Obvious! right? ......