Modem connection

I have a Dell Dimension 2400 with Windows xp home edition, using Intel®537EPV9x DFPI modem. When I dial up, I often get the messages "The phone line is in use" and "There was no dial tone." even though I know there was a dial tone. some times I can connect after one or a few redials. Some times I cannot connect after many redials. Sometimes those messages are followwed by "Your password is not recognized on the domain", "A device is not functioning" or "The server unexpectedly disconnected" I unchecked the "Wait for dial tone" option in the modem properties site. However I usually (not always) get those "no dial tone" responses. My question is: Should this happen after I have unchecked the "wait for dial tone" box? Thank you for your assistance.

After a set period of time the modem software will provide a notification if no dial tone is detected. You should recheck that box or you will most likely get errors even if everything is working right as it sometimes takes a fraction of a second to get a dial tone. Check the phone line going into the computer. Is it plugged in tight? Can you lightly pull on it and have it stay connected? Do the same at the phone jack connection on the wall. If it seems ok there, unplug the line from the computer and plug it into a phone. Listen to the dial tone on the phone as you lightly wiggle the wire where it goes into the jack on the wall. If the dial tone is not steady then there may be a problem with the wire or the jack. Try the same wiggle test with the end that is plugged into the phone. You can get a new piece of phone line, all set up, very cheap so try that and see if it helps. Also, cordless phones can cause interference that might disrupt the modem, even if they are not in use. Keep any cordless phones and bases as far away from the computer as you can.