increase the shutdown speed of PC

Increasing XP shutdown speed
Increasing shutdown speed by reducing wait times:

Windows XP stores a couple of values in its registry which are responsible for determining how long to wait before shutting down (killing) open applications and services once the shutdown command has been given.

By editing these two settings and changing them to lower values, you can considerably decrease the amount of time that Windows XP needs to successfully shut itself down. The first part of this tweak deals with setting the amount of time Windows will take to kill open applications on shutdown.

Open REGEDIT and navigate to 'HKEY_CURRENT_USER\Control Panel\Desktop\'
Highlight the 'WaitToKillAppTimeout' value.
Set it to '1000' (the default should be 20000).
Now highlight the 'HungAppTimeout' value
Set it to '1000' also.

------------------------------------------------------------------
FOR ALL USERS


Increasing shutdown speed by reducing wait times :

The second part of this tip changes the same settings, this time for all users on the system.

Open REGEDIT and navigate to 'HKEY_USERS\.DEFAULT\Control Panel\Desktop'
Highlight the 'WaitToKillAppTimeout' value.
Set it to '1000' (the default should be 20000).
Now highlight the 'HungAppTimeout' value.
Set it to '1000' also.