I have met many people like myself that run Oracle on their Windows XP boxes to play around and have "fun".  We all like to turn it on only when it is needed, and we want to turn on the fewest number of these resource-intensive services.  Following are the services I turn on when I want to run Oracle locally:

OracleService<dbname>
Oracle<oracle home>TNSListener

Note:
- I usually go into the Windows Services management tool and "Disable" these services after each use.  This also serves as a visual flag to remind me which services I need to start.