At work we have this simulator executable that works fine on desktop
computers.  It will open but not run on laptop computers. One person
mentioned they thought disabling the serial port on the laptop would
make it work but no one seems to know how to do that.  Any suggestions
for disabling a serial port without messing up my laptop to test this
theory?  I have a dell inspiron 5100 with windows xp pro os.

How about disabling it in Hardware Manager?

I don't know how to do that as far as disabling it. I didn't know if
you could just disable it somehow without messing up the configuration
for the port. That is why I wanted to see if there was a way to
disable it and then enable it when not using that software simulator.

I think calvinso has a good idea.  Have you tried the hardware manager
idea?  Right click on My Computer and select Properties.  Click on the
Hardware tab and then Device Manager.  Scroll down to find the port,
right click on the port and then select Disable.  You can always
Enable it again later through the same menus.

I suggest tryone the advice from needsominfo first, but if that does
not work you may have to go into the BIOS of the computer and trying
to see if it will allow you to disable serial port that way. This in
effect turns off the device at the hardware level, while in Windows
you turn it off on the software level. Disabling it in the BIOS may be
more effective, and you can turn it back on later if you need to.