I have one older computer with Windows 98 second editiion. This is all I have ever found out about this problem::
"Common Causes of Shutdown Problems
Shutdown problems in Windows 98 Second Edition can be caused by any of the following issues: • The Fast Shutdown registry key is enabled.
• There is a damaged Exit Windows sound file.
• A program or terminate-and-stay-resident (TSR) program may not close correctly.
• An incompatible, damaged, or conflicting device driver is loaded.
• There is an incompatible Advanced Power Management (APM) or Advanced Configuration and Power Interface (ACPI) setting.
• There is an incompatible Basic Input/Output System (BIOS) configuration setting.
• The computer contains incorrectly configured or damaged hardware.
• There is a video adapter that is not assigned an IRQ in real mode
"
Of course this was found
HERE.
Don't know if this covers anything that you guys don't know?