How do you set a com to become active;have the computer recongize it?

ok, you geekheads, lets try a different angle. How do I set my com ports to become active and have the computer recongize it? I have done the system, modem, hardware, device mgr, advance setting. I put the modem in com#3 and when I try to put it back to com#4 it will not take it. Now, the problem is when I go to turn the computer off it KICKS INTO RESTART ON THE TURN OFF BUTTON. WHAT THE ....! Any more ideas?
The Gypsy.

 

You may need to go into the BIOS settings on your computer and enable or disable one or both serial ports on the motherboard.

If you are installing a modem card on COM3 in Windows, you may need to disable serial port 1 in the motherboard's BIOS so that it won't conflict with the serial port that is provided by the modem card. If you want it on COM4, try disabling serial port 2. Or disable both motherboard serial ports if they're not in use.

COM1 and COM3 usually share serial port 1 and IRQ4. COM 2 and 4 are usually serviced by serial port 2 and IRQ3. If two devices try to use the same IRQ, the wrong interrupt handler may get called, with unpredictable results.

You haven't said which version of Windows you're using. Earlier versions didn't like setting up serial devices on a COM port with a number that was higher than an unused COM port. If you think that's a possibility, try using COM1 or 2 for the modem.

For a modem, set it up on the lowest-numbered IRQ that you can. Interrupts are serviced in the order of the IRQ line number, and modems generate a LOT of interrupts that need to be serviced quickly. That isn't a problem with the processors now in use.

IRQ3 is usually the best-available option; that usually dictates COM 2 or 4 for the modem. But with Windows XP, you may not have much control over how the modem gets set up. Windows will do its own thing quite well when the hardware is properly configured, which probably means getting the motherboard serial ports out of the way.