First, disconnect the printer, turn it off and unplug it from both power and computer. Leave it that way throughout the following, until you are instructed to connect it up again by the installation software routine (or, at least, by that routine having completely ended and finished and exited etc.)
So: turn off, unplug, unplug your printer.
Go to your computer, to the Start button, then to Control Panel, and remove all entries for your printer and its series in Devices And Printers, by clicking on each icon (or entry) and deleting. (In this case, if there are any scanners shown, or any HP devices, select and then delete those, also.)
Then go to Control Panel, Programs, Programs And Features, and use Uninstall (or Change) to get rid of all programs specific to your printer.
Then, reboot your computer: shut it down and start it up again.
Then, go to
and click once on the link for
HP Officejet 4650 series Full Feature Software and Drivers
then click on the red Download button and follow the download process, getting the driver onto your disk, and completing the download and then starting the driver installation program and following through the process.
That will replace the drivers.
But if you still have problems with your printer, try also getting and using, from that page, under the heading of
Utilities - Diagnostic Tools
the HP Print & Scan Doctor,
which when run on your computer, may help determine what is wrong.
Let me know how things turn out - and if there is a problem at any point, please just stop and let me know, and I will help you further.