Some things to try, in no particular order, to speed up your modem and/or Internet connections:

Get a better modem.
There are a lot of junk modems out there. You may have gotten one.
Unfortunately, subpar modems, as well as their accompanying drivers - the files that regulate the way the modem interacts with other parts of the computer - are not up to the rigors of Internet communications.
Check modem reviews in computer magazines or one of these sites:
http://www.zd.net
http://www.cnet.com
If your modem is not listed as a top performer, replace it.
Update your modem driver.
Even if you have a top-of-the-line modem, it may be using a driver that may have met the standards of its day, but is now outmoded.
Visit the Web site of the modem's manufacturer, and check whether there is a newer, better driver available.
Have your phone line checked.
In many cases, slow Internet connections can be traced to a noisy phone line. The phone company may be able to clean it up for you.
Double-check your connection speed setting.
Click on the "My Computer" icon, then right-click on the Dial-up Networking icon for your Internet service provider. Click on "Properties."
Click on the "Configure" button in the "Connect using" section.
In the configuration dialog box, your "Maximum speed" setting should be set at 57600.
If not, click on the arrow on the right of the window within the "Maximum speed" section and select 57600.
The box next to the line reading "Only connect at this speed" should not be checked.
According to some experts, setting the bits-per-second rate on your modem to 115200 can speed up connectivity.
You can choose that setting in the "Maximum speed" section as well.
Experiment. More than likely, your Internet service provider has several access numbers in your area. Try the various numbers - after making sure that no toll charges are involved, of course. You may just find the one that gives you faster access speeds.
Try updating the modem's firmware - the software residing within your modem - by downloading it from the Web site maintained by the modem's maker.
The Web site should have information detailing whether your modem can be updated in this fashion.
Also try this, in the sequence outlined:
Go to "Start/Settings/Control Panel." Click on "Modems." Highlight your modem. Click on "Properties." Click on the "Connection" tab. Click on the "Advanced" button.
Click on the box next to "Use error control" to remove the check mark. "OK" your way out.
Freeing the modem of the need to deal with errors may speed things up.

Last word: No matter what you do, you may not be able to get your connections to fly faster than 43K to 48K, and certainly no faster than 53K.