for drivers go to http://www.usa.canon.com
you will find every driver for free download
after you have made this upload add printer but unziping each file and setting it on your system
under all Programs you will see new programs associated with your downloaded files Next, add Printer from "Start" add printer menu it will auto upload W8400 Printer.
make sure yout canon is "ON" and pluged to your "PC"
after this has uploaded you will see from the programs now downloaded one program called imagePROGRAPH firmware update too, click on the icon close all programs less this page and the program itself click OK and it will search for target printer, if the unit is conected it should show data of the W8400 Canon Printer including firmware, if the firmware reads 2.15 and the year you are in is 2011, then you are uptodate for now, if it reads a smaller number then do the next step, which is goto you printer and switch it off, then press (OK + stop/eject + information) do not let go of the bottons and switch unit ON.
do not let go untill you see GREEN online light come on
you now will see on the screen DOWNLOAD MODE send firmware. walk back to your PC and in the above menu you will see "file - view - printer - firmware - help" click on firmware and send the file.
Make yourself a coffee, by the time you drank it the screen should say load finished and switch off
do that and re start normaly the firmware should have updated. and 2.03 now read 2.15 any other number above this and you may have the wrong frimware.
If the unit still reads Printhead Error, and you see the ink is running okay, not block then it may be something wrong with the heads but if it is blocked place in hot water and you will see the ink flow
dry with paper towel by preding not sliding if you have print head problems still, check circuit conection if there is power comming to the head,