My r300 stopped working. i changed an ink cartridge and it started printing stuff I'd forgotten about, so I went to the control panel and must have deleted it. I added it back but it says there is an error. Please help!!!

You should be able to change cartridges. It may be hard to determine what is wrong with the display but look for loose connectors on the back of the display, the controller board, etc.

Follow these steps to clean the print head from the printer's control panel:
1. Make sure the printer is turned on but not printing, and the red
b error light is off.
If the red light is flashing or on, you may need to replace the ink cartridge.
2. Press the down button to highlight More Options, then press OK.
3. Use the up or down button to highlight Head Cleaning, then press OK.
4. To begin cleaning, press OK.
While cleaning, the printer makes noise and you see a progress bar on the control panel
display. Cleaning takes about 30 seconds.
Caution: Do not turn off the printer or interrupt the cleaning process.
5. When the cleaning is done, run a nozzle check to confirm the print head nozzles are
clean.
Make sure letter-size plain paper is loaded in the printer, then press Stop. The nozzle check pattern prints.
6. If the pattern has gaps or missing dots, press Stop to clean the print head again.
If the nozzle check pattern looks correct, press OK to finish.

Note: Run nozzle check at least three consecutive times. If you do not see any improvement and you have replaced the ink cartridges, your product may require service.

If you're using Windows,
XP : Click Start, go to Control Panel > Printers and Faxes Right click on your printer, click Printing Preferences, click Ink Cartridge Replacement. Follow the instructions.
Vista : Click Start, go to Control Panel > Hardware and Sound > Printers Right click on your printer, click Printing Preferences, click Ink Cartridge Replacement. Follow the instructions.
7 : Click Start, go to Control Panel > Hardware and Sound > Devices and Printers Right click on your printer, click Printing Preferences, click Ink Cartridge Replacement. Follow the instructions.

XP :Click Start, go to Control Panel > Printers and Faxes Right Click on your printer and click Printing Preferences. Click Maintenance tab, click Ink Cartridge Replacement. Follow the instructions. --- Vista : Click Start, go to Control Panel > Hardware and Sound > Printers Right Click on your printer and click Printing Preferences. Click Maintenance tab, click Ink Cartridge Replacement. Follow the instructions. --- 7 : Click Start, go to Control Panel > Hardware and Sound > Devices and Printers Right Click on your printer and click Printing Preferences. Click Maintenance tab, click Ink Cartridge Replacement. Follow the instructions.

1. open a document. 2. control-P - shortcut for print. then click properties, click maintenance, then click head cleaning. after this print check pattern. continue doing this until your light magenta and yellow ink gets clearer. if it didn't work replace your light magenta and yellow cartridge.

go to the printer setting under control panel, right click on the icon then properties..you can check the ink level there...normally if your printer blinks and ask for a new cartridge..better follow what the printer says... : >

I had the same problem after changing the black ink cartridge. I went to Control Panel of my computer, chose Printers, then Canon Inkjet. Chose Properties, then Maintenance, the Deep Cleaning. NOW my printer is working!!

This is independent of every printing ink type and there usually is good instructions with the refills you get for the ink cartridge.
Have you purchased a refill cartridge?
Assuming not - there are 2 options; one is to buy a replacement ink tank same as the one which has run out, the other is to buy refill inks which you "inject" into your existing cartridge.
Personally, I use refill inks, as the running cost is about 1/5th of buying new and I have a copious supply of print cartridges. Some people really don't like using refills, because it's easy to get stuck with a refill kit and the ink cartridge dies or heads become clogged, forcing you to buy a new cartridge anyway. Your gamble, ahh, I mean choice....
I doubt it's computer/CPU related, but, just in case, you could try going to Start>Control Panels>Administrative tools. Double-click on 'Services', a window opens that show all the optional services for your Windows, some running, some not. Scroll down to "Print Spooler" and across from that you'll see "Started", 'Right-click' on this and change it to "Stop". This stops any printing instances that are stuck, jammed, frozen, just will not go away. Now 'Right-click on "Stopped" and change it back to "Start", close your open windows and try printing again.
If you go to Start>Control Panel>Printers and 'Right-click' on the printer in question, go down to "Properties" and when that opens click on "Print a test page" button. If you machine fails to print, a dialog box/window will open to help you troubleshoot it - must admit the questions asked are very basic and it has never helped me but may open some ideas for you.
Please let us know how it went.

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With the power on and the lid up, click on the red stop (left panel). You will notice the cartridges move to the left and then they come back and stop halfway. Afterwards you should be able to slide the cartridges manually with your hand to the larger area on the right where you could do the cartridge change. Once you've moved it to that area just the lift the cover where the arrow is.

Buy a new ink Cartridge.
Take it out shake it a bit, put it back, if it prints darker for a little bit. You need a new ink cartridge..