Where do I get a new printhead for an pixma mp620. I have an error message that says B200 for error. From what I've read it says that should fix the problem.

Check if the drivers for the printer are installed and working properly on the computer. All the devices which are connected to the computer require a set of drivers to be installed on the computer. If the appropriate drivers are not installed on the computer then the device will not work properly. To check if the drivers are installed and working on the computer, right click on My computer and select Device manager. Highlight the installed printer. If there are any caution signs then follow the troubleshooting procedure. If troubleshooting does not help then try and update the drivers for the printer and see if it works.

The error B200 refers to an overheat error of the printhead. however the head usually damages the logic board and both require replacing as a pair. Sorry but probably not an economical repair and a replacement machine is better.

Probably not. It is likely that the gear train has dropped out of sequence, and that is extremely difficult to reset.

Unplug the printer for at least 5 minutes to see if it will clear that error message. The b200 error message is referring to the printhead overheating. It is possible that a printhead nozzle burned out while printing a page and ink ran out. No ink flowing through a nozzle can cause it to overheat and damage it. If waiting for the 5 minute power down doesn't do it, you may have to purchase a new printhead and also check to make sure that you have new ink cartridges.

Per Canon's website, and this just worked for my mp620:
Turn the printer on.
Open the cover.
Remove the ink cartridges.
Remove the printhead.
Re-install the above (this resets the printhead).
Close the cover.
Printer should initialize and go to home menu screen.

I replaced my old MP620 with a new one. Decided to use the partially used cartridges up before replacing with the new ones in the box. Next day the yellow was empty, so I replaced it with the brand new yellow cartridge shipped with the printer. Then this error message. Thank God for this website because I read some of the blogs and decided to take the cartridges out and reseat the print head. Then I put the same cartridges back in. This put the printer automatically into "cleaning the print head" mode and now no error message!

B200 IS BAD PRINTHEAD. i TRIED TO CLEAN CLOGS BUT IN THE END THE FIX WILL BE TO (REPLACE PRINTHEAD) IF UNCLOGGING PRINTHEAD OF DRY INK DOES NOT WORK. YOU CAN UNCLOG BY USING A PRINTHEAD CLEAMING KIT, BUT IF THIS DOES NOT WORK REPLACE HEAD. EBAY WAS CHEAP FOR ME 25 BUCKS PRINTER IS WORKING AGAIN.

Very simple solution: When the pixma mp620 screen shows error U130, Hold down the stop (red triangle) key for about 7 - 10 seconds. This overrides/turns off the ink monitoring function. The printer will begin "thinking" for a bit and then start printing. Note: you may have to do this seperately for each color. You'll also notice that when the lid is open and the cartridges are in position for changing, the cartridges that used to be "out" are no longer flashing red, nor a stead red. They are dark.

unplug the printer from all source of power supply ,leave it for like 15min then plug it back.make sure the printer is proberly connected

That is a printhead error, sounds like you will need that new printhead.