In win98se, if you enable fast shutdown (change the data of the registry value FastReboot in HKEY_LOCAL_MACHINE\SYSTEM\currentControlSet\Control\Shutdown to 1, or uncheck Disable Fast Shutdown in msconfig advanced options), your pc will restart when you turn if off normally. M$ released a patch called Windows 98 SE Shutdown Supplement to fix this bug. But in fact, this patch doesn't fix the bug, only updates some drivers related to battery and power management, and hides the Disable Fast Shutdown option in msconfig by replacing msconfig to a newer version. if you set the above registry value data to 1 after installing this patch, you will find that Windows still restarts when you turn off your pc.

In my observation, the reason why this bug still exists when this patch is installed is that the fast shutdown bug is in the file reboot.vxd, which is integrated to vmm32.vxd when the first time win9x starts during Setup. And none of the win9x updates (including security updates, non-security updates, and hotfixes) update this file until their eol. So just replace 98se's reboot.vxd with the one in 98fe rtm, the fast shutdown bug in 98se is fixed.

Additionally, the first updated reboot.vxd (version number > 4.10.1998) is in the build 2150 (98se beta2). from this version of reboot.vxd, the fast shutdown bug introduced. the version number of this file in the previous builds of 98se beta is 4.10.1998, actually it's the same file as the one in 98fe rtm.

Edited August 22, 20233 yr by xkai

Win98fe also has a fast shutdown bug that Windows can't soft power off itself when fast shutdown is disabled on an acpi-based pc. This is due to an incomplete support in its acpi driver windows\system\acpi.sys. Just replace this file with the one in 98se (build 2170 or higher) to fix this bug.