Let's start again.
Go to my link above.
Select your operating system.
Click 'Search'.
Click on 'Full Driver & Software Package'
Click 'Agree to the EULA and Download'.
Save the .exe file to anywhere convenient on your PC. '(Downloads' is the most obvious place)
However DON'T run that file yet.
Go here and go through the same procedure to download the Uninstall Tool:
http://support.brother.com/g/b/midlink_os.aspx?c=gb&lang=en&prod=dcp135c_eu_as&site=pc&type3=39&orgc=gb&orglang=en&orgprod=dcp135c_eu_as&targetpage=18
Run the Uninstall Tool.
Disconnect your printer from your computer.
Run the first file that you downloaded.
That will create a new folder inside 'Downloads' (or wherever you placed the file). Double-click on it to open it.
Look for the folder that includes the model number of your printer and double-click on it.
Double-click on Setup.exe
Follow the on-screen instructions.
ALTERNATIVELY:
If you've still got the disk that came with your printer (and don't mind that the drivers on it might not be the most up to date ones), simply download and run the uninstall tool (from above), disconnect your printer, insert the disk into your computer's drive and follow the instructions from there.