Was having same problem, first thing I did was to do a virus scan using
Norton AnitVirus 2005. NAV Found 10 files, all related to NavExcel Search
Toolbar (not sure how it got on my computer). I allowed NAV to
delete/quarantine these files. To my surprise my shutdown problem was fixed.

"Vista" wrote:

> XP Pro SP2 restarts instead of shutting down. has started recently and none
> of the standard solutions have helped (DEP, off; unchecked Auto Restart; all
> patches up-to-date, no virus/ adware issue, APM - not available). Checked
> BIOS and could find nothing wrong (BIOS was updated 6-8 months back without
> problems).
>
> Problem started after I updated/ installed a few programs - the first was
> installing the trial version of Intervideo's HomeTheater (followed by
> uninstalling). I later updated my Nero 6 Burning ROM to the latest NERO 6
> Reloaded. PowerDVD6 and WinDVR3 were preinstalled (if this info helps).
>
> I suspect driver conflict for lack of any other suitable explanation.
>
> My config is P4 2.8GHz with a 160GB SATA HDD and 1GB DDR RAM, NVIDIA 5200
> AGP Graphics card., 2 x DVD+/- R/RW/1xRAM drives.
>