Before attempting more involved troubleshooting procedures on your HP Photosmart C4480 All-In-One printer, try resetting the unit. According to HP support documents, resetting your Photosmart C4480 can clear up a number of troubleshooting issues you are having with the printer like response lags, power issues and printing errors.
Press the "Power" button to turn off the printer.
Remove the power cord from the back of the C4480.
Wait five seconds, then plug the power cord back into the unit.
Press the "On" button to turn the printer back on.