If you are using motorolla or rockwell modems then you might encounter problems after you have installed their windows 2000 drivers on XP pro.One such problem is the delay between connecting and disconnecting from your respective ISPs.On most occasions the pc gets stuck and the system needs to be restarted.In order to cop with it, try the following tweak.But first backup your registry as a precaution ;though there will be no problems.
1)goto run and type regedit
2)seclect HKEY current user/remote access/profile/"your isp"
3)Change the value of disconnect idle time from 14 to 0.
This will solve your problem.