Your problem is far more likely to be related to a need for head cleaning than it is to a need for realignment. Fortunately there's a standard way to access the relevant settings for any make of printer:
Go to Start > Devices and Printers. (That's how you do the first bit with Windows 7. There might be minor differences with other version of Windows).
RIGHT-click on the icon for your printer.
Select 'Printer Properties'. (NB: NOT just 'Properties')
Click the 'Maintenance' tab.
You should then see the options offered by the manufacturer of your printer which, for a Canon, should include both 'cleaning' and 'deep cleaning'. Give the former a go but don't be surprised if it doesn't completely fix the problem. Then, if required, try the 'deep cleaning' option but, again, don't panic if it doesn't immediately work. Simply repeat until you can print out a perfect test page.