how can i fix my pacific television?

On my pacific television you can enter a key code that works like a pincode that locks the tv unless you enter the key code. I accidently pressed this function from the menu button but during set up i purposely did not enter a key code but someone one has been set. Everytime i turn on the TV it asks me for a key code but i dont know what it is because i didnt set one. Is there any way to reset the TV so i can get rid of this really annoying problem? Any help would be greatly appreciated. The TV is stocked by asda and is about 4 years old (isn't a plasma or flatscreen or anything)