If so, what have you done to the machine? Have you tried system restore?

BTW, WEP is old hat and can be hacked in about 20 seconds. You need to change to WPA/WPA2.

You might also try tweaking it. Go here http://www.broadbandreports.com/tools Run their speed test, make note of the results. Not run the Tweak test and note the recommendations. Run Dr. TCP and make the adjustments. Reboot and run the test again.