My husband's USR external serial modem was fried during a lightning storm this week (despite it and the line being connected to a surge protector). We bought a Creative Modem Blaster V.92 (USB) to replace it. The new modem worked fine -- until we restarted the system. Now he gets 'Error 633: modem is already in use' whenever he tries to dial in to his ISP. He has 2 USB ports. Using either gives the same error. The only thing that fixes it and allows him to get online again is a reinstall of the modem/drivers...but we live in Central FL, and at this time of year we have to shut our computers off nearly every day due to thunderstorms. Reinstalling the modem/drivers each time is NOT the optimal resolution. I've scoured the net for a permanent fix to this problem, tried everything -- even the suggestions from this site -- but no joy. It is not peculiar to Creative modems. The Windows KB articles are no help; there's no Palm software installed on his machine, and the telephon.ini/tapiini.exe fix does not pertain to XP. There is nothing new on his computer besides the modem, and no software that might be grabbing the ports on start-up. Other users who've been told to reinstall XP report mixed, mostly negative, results. I'm quickly coming to the conclusion that this might be a USB port problem, i.e. the two current ports are old and cheap and perhaps need upgrading. But I thought I'd post this to see if anyone has any other ideas before I start taking his computer apart! Any suggestions welcome and appreciated.

Did you see this one? http://support.microsoft.com/default.aspx?scid=kb;%5BLN%5D;822112

Thanks, but that's not the same problem. I've discovered more now that I've had time to do some process of elimination work. It's a bit of a DOH! that I left this info out before, but I still can't work out what's going wrong: The computer has two USB ports. Previously they were used by a Lexmark Z45 USB printer and a USB scanner, and they got along quite happily. When we got the modem, we unplugged the scanner and connected the modem to the freed port. All was well -- the modem connected -- until the system was restarted. Then DUN error 633 popped up. Once this happens the modem cannot make a connection until one of two things happen: 1) The printer/drivers are removed and the system is restarted; or 2) The modem/drivers are reinstalled. I've since tried connecting an a/c powered USB hub, thinking the ports might be underpowered to handle both the modem and printer. Same story. If the printer drivers load after a restart, the modem gives Error 633. Although there are two ports (or 5 with the USB hub), it's as if the Lexmark printer grabs all of them and denies the modem access...which mystifies me, 'cause the SCANNER and printer work fine together. Any other ideas?

Have you removed the OLD modems software?drivers? Is XP still looking for your OLD modem?

I'm facing exactly the SAME problem and symptom. Even tried reinstalling, it was working fine until I plug in the USB printer (Lexmark) and keyboard. Then the Error 633 symptons will appear. When driver is removed and reinstall it'll work for the first time, once restarted it'll hit the problem again. Hope that someone can help! TQ.