The Windows update service takes about 10MB of RAM, but is used about once every month.
What a waste, espcially if running on a Netbook or low-end laptop where RAM is at a premium.
It's easy to turn off the service using the Services.msc tool, but then for some reason the Windows Updates website doesn't know how to turn it back on as needed. Instead, you need a batch file which starts up the service and then shuts it down as soon as the update is over. Likewise, the BITS service is only used by Windows Update, so it too can be enabled just as needed. The problem I ran into, however, is that even when Windows Update service is running Windows update may not be able to detect it, and will return an erronous 0x8DDD0018 error. This is solved by running regsvr32.exe wuaueng.dll.
The final batch file is as follows:
net start wuauserv
regsvr32.exe wuaueng.dll /s
net start BITS
start /wait iexplore update.microsoft.com
net stop wuauserv
net stop BITS