i think its just "sfc" in previous versions of windows.
is windows up to date? click here
if its just the dial up connection that is slow then try at different times of day as it could just be congestion.also try a speed test click here what are the results?
try plugging the modem directly into the main phone box and do not use an extension or extension socket.maybe also try updating the drivers for the modem if you know the model.