By default the USB polling interval is once every millisecond (ms). Even if no USB devices are connected the polling operation is still performed and the processor may not be able to enter power-saving state. Use this tweak to increase the polling interval.
Open your registry and find the key below for your Windows version.
Windows 98 [...]

If you require additional information about a device that is not typically displayed in Device Manager, you can use this tweak to make Device Manager show detailed device information.
Open your registry and find or create the key below.
Create a new String value, or modify the existing value, called “DEVMGR_SHOW_DETAILS” and set it according to the value [...]

This setting controls whether Windows should automatically power down or reboot your computer once it has finished the shutdown process.
Open your registry and find the key below.
Create a new string value, or modify the existing value, called PowerdownAfterShutdown and set it to “1” to power off the computer at shutdown, or “0” to reboot.
Restart Windows for [...]

Windows XP includes support for Universal Plug and Play (UnPnP) which allows UnPnP devices to be connected over a network. There are currently limited UnPnP devices available and due to a recent security flaw it may be advisable to disable these services.
Disable Universal Plug and Play Device Host
Open your registry and find the key [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\upnphost]. [...]