I have cctv up in my home 18 months now but it is only showing a quarter of the scene and hard disk fail comes up can anyone tell me what I can do to fix this please.
I turned it off and then on again but still the same where would I get a replacement hard disc
It sounds like you have a 4-channel (4 camera) digital video recorder with an internal hard drive to record the video captured by the cameras.
The surveillance DVR hard drive needs to be replaced (that should resolve the "hard disc fail" error message. It is likely that the DVR may need to be replaced, too… which is why you can only see 1 of the 4 cameras.
BUT, you did not tell us which system (manufacturer or model number) so there is no way to know for sure. Try powering down the DVR, count to 10 and turn the power on… That just might fix everything - if not, at least you tried and then you know to replace it.
Since we cannot see what you see, it is challenging to troubleshoot.