The HP 840C is a deskjet printer manufactured by Hewlett Packard. Unlike laser jet printers, which use toner to create images, the HP 840C uses standard black and white and colour ink cartridges. If you're having problems with your HP 840C, it is likely due to a few recurring issues that are known to happen with computer printers of this type running on the Windows operating system.
If the colours on the documents that your HP deskjet printer is printing are incorrect, this is a prime indication that you are low on ink. Go to the store and buy replacement cartridges, specifically designed to fit the 840c, and install them into your printer. Restart the printer to accept the new ink and try to print your document again.
Click "Start" and choose "Printers and Faxes" or "Printers." Right-click on the icon for your HP deskjet printer and click "Properties." Review the settings and make sure that everything is correct based on the document that you're trying to print. Make sure that both the paper size and orientation are correct, as well as anything else that relates to the specific problem that you're having.
Put your HP deskjet printer's driver CD-ROM into your computer. When the HP deskjet printer driver set-up wizard starts, click "Next" to reinstall the device driver. Restart your computer and attempt to print your document again. A faulty device driver could lead to image problems with an HP deskjet printer, so reinstalling it should fix any issues that you have been experiencing.
Clean your HP 840C. This doesn't mean that you have to get out a rag and cleaning solution and perform the task yourself. The HP 840C includes an automated cleaning utility that will perform the task for you. Click "Start," select "All Programs" and open the HP Toolbox with its icon. Click "Printer Services" and select "Clean the print cartridges." A new window will open. Click "Next" and the HP 840C will automatically perform routine maintenance on itself, cleaning the heads of the ink cartridges inside the unit. You can perform this steps as many times as you need until the problem that you're having is corrected.