If you have a serial mouse on COM1 or COM2 that occasional fails to be detected at startup, you can just fiddle with connector, without the need to reboot, by adding value entry OverrideHardwareBitstring as a type REG_DWORD to:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Sermouse\Parameters
A data value of 1 indicates that the mouse is installed on COM1 and a data value of 2 specifies COM2.
This entry causes the driver to load, even if the mouse is not detected.