This is an unusual use of IRQ for COM3, because by default COM3 uses IRQ4 on most X86 motherboards/chipsets that I know of.
You may need to reassign another IRQ [10 in your case] to COM3 if it will allow you to do so, from Control Panel -> System -> Device Manager tab -> Ports -> COM3 [highlight it + click Properties button near bottom] -> if IRQ is anything else but 10, you may need to access the Reserve Resources dialog:
Control Panel -> System -> Device Manager tab -> double-click on My Computer -> Reserve Resources tab -> Interrupt Request (IRQ) box must be checked -> click Add button at bottom -> scroll to 10 -> click OK/Apply [twice] -> reboot.
FYI:
Might be a hardware conflict [you will see a red X or yellow ? in Device Manager list] if IRQ10 is already used by another hardware device and is not properly shared.
To make sure IRQs are shared in Win95/98/ME, must enable IRQ Steering:
Control Panel -> System -> Device Manager tab -> double-click System Devices -> double-click PCI Bus -> IRQ Steering tab -> make sure Use IRQ Steering box is checked -> reboot if you changed this setting.
Another thing to do [if possible]:
If your modem card allows to change IRQs and/or COM ports from the card itself, like DIP switches or jumpers, you may want to do so. Try to change from COM3 to [for example] COM1, or if that doesn't work, try to change COM3 IRQ number to something else, usually selecting an IRQ number you know is not in use by any other hardware device.
The list of used IRQs:
Control Panel -> System -> Device Manager tab -> double-click on My Computer -> View Resources tab -> Interrupt Request (IRQ) box must be checked -> look at the list.
More stuff to try:
http://www.mdgx.com/newtip4.htm#KILLERhttp://www.mdgx.com/last2.htm#FASThttp://www.mdgx.com/newtip6.htm#COMASSIGNHope this helps.