Dial up has many breakdown points. Make sure you are going straight into the line, and not a splitter. First, try a few different access numbers. If one is better than the other, there you go...
If they're all the same, ask your local telephone company to do a line test, they can do it from their offices, takes only a few minutes.
As for Windows dial up tuning, there are 3 things I recommend. These are assuming you are using a straight dial up connection, and not some cheap ISP with horribly written software like AOL or Netzero. Even AT&T installs software by default, I recommend dumping the software and going with a straight dial up connectoid.
1. Tune and configure your modem.
Go to the modem's properties in the control panel, lower the maximum speed to 57600. You can also try a modem initialization string, more info can be found at
2. Recreate your dial up connection (connectoid).
Go to My Computer>Dial Up Networking. Add a new connection, type in the access number, and finish. When its done and listed, right click on it and go to properties. Make sure Log on to Network is unchecked, and uncheck IPX/SPX and NetBEUI. Only TCP/IP should be used. Now, go the server types tab, and enter your ISPs DNS server addresses here, you can call them for them if you don't have them.
Matt J.