I was running XP pro on my laptop. I only use the modem when I am on the road other wise I use my home network for internet and email access. I was on a trip this past week and everytime I went to use the modem, the dial up connection said no modem detected. Checked the device manager and it was there, it would do a good check, but would not connect. I could uninstall it, and reboot and it would work fine. Until the next time when I turned the laptop back on, then I would have to repeat the proceedure. Put Win2000 back on it and it works fine. Any ideas???

Hello & welcome to the forum's.
I believe this is a documented problem and one that a few people have reported.
Although it doesn't happen to me every time, if I do say three or four dial-up sessions, when I try again sometimes it reports no modem found and I have to do a re-boot.
It doesn't happen after a single dial-up session, so it sounds like you have the same problem, just a bit more severe.
Would expect SP1 to eventually fix it, not aware of any pre-SP1 Hotfix that addresses this issue.