I can't know this one. No make/model/website of the modem is noted. Sadly with PCI modems diving under 10 bucks, your best choice may be to get a new modem with Windows ME drivers...
I posted earlier under Modem won't work. I could not get the new modem to work. So I installed the old modem back in and realized what the problem is. The old modem is on Com3. I pull that one out and put the new one in. Install the driver and it puts the new modem in Com1. It does not give me the option of Com3 like the old modem. Com1 says "no modem installed". How do I put the new modem setting on Com3?