How to reset the Canon MP150 after a refill (Step 10 concerns refill; instructions below the steps):
Method1 (Safe Factory Method):
1) Disconnect the printer’s power outlet
2) Press and hold the power button while connecting the power outlet back.
3) While still holding down the power button, press the reset button twice.(red circle with a triangle)
4) Release the power button
The printer takes about 10 seconds to show the number 0.
5) Press + to change the value from 0 to 1.
6) When this value is 1, press colour button; this will light up two leds.
One is for plain paper and the other for photo paper. At this point is feed the printer with paper.
7) Press the power button twice and the printer will print a some stuff (if this page doesn't print by itself, press the "color" button once and the test page will print). Don’t worry much about the printed material. I got some stripped lines and some numbers. I believe that my colour cartridge is clogged which is why I got the green strips.
When you print this sheet the value in the display returns to zero.
8 ) Open the printer cover cover (not the scanner cover) and remove the cartridges. With the printer still open, disconnect the power outlet.
9) Close the lid and turn on the printer.
10) Refill cartridges and place them back in their nice little abode in the printer.