How do I disable mouse detection on a COM port (for UPS usage)?

Start a command prompt (Start - Run - Command)

Move to the boot partition
c:
cd

Change the attributes of boot.ini so it can be edited
attrib boot.ini -r -s

Edit the file (edit boot.ini) and for each line with multi(x) (for IDE) and scsi(x) (for SCSI) drives add at the end
/noserialmice=comx ----------------------- where x is the com port number
Exit edit

Set the permissions back on boot.ini
attrib boot.ini +r +s

Shutdown NT and power off

Attach the UPS

Boot the machine and start NT, and NTDETECT will no longer try and search for a mouse on that com port