I've got a batch file I use just for this. (we had issues a while back and the DNS needed to be flushed)
I don't have it with me, but it was something along the lines of.....
@echo off
cls
echo.
echo.
echo. Pressing a key will flush your DNS
echo.
echo.
echo.
pause>nul
ipconfig /flushdns
ping localhost>nul
ipconfig /registerdns
echo.
echo.
echo. DNS is now flushed. Please see above for any errors
echo.
echo.
echo.
pause
exit
hope it helps.