1) printers...as in more than one ???? if they are plugged in through USB ports then it is a good possibility that since all went out at same time that the USB hub or controller went bad or lost the drivers or you have a bad connecting cable(s)
a) if you are using a USB hub to connect the printers...try using a USB port directly on your computer to see if they will work now.
b) start > control panel > system > hardware tab > device manager and check to see if you have a !or ? next to the USB controller or possibly an unknownpiece of hardware....you will need to reinstall the usb drivers
c) try a different connecting cable
*****if you are using a paralell port for your connection then the proceedure for trouble shooting it would be the same as ....b...above.
***** networking print servers would have to be checked out by a network adminastrator to asure proper connectivity.
***** If the printer died then it will also show the same warning.
as a last resort uninstall the printers and using the manufacturer's installation proceedures....re-install the printer from scratch.
Use the uninstall driver in device manager to remove the old driver(s) then unplug the printer and use the add/remove application in control panel to uninstall all the old printer files.