I am working on a MacBook Pro A1278

Originally I had a problem with the MacBook running exceptionally slow. It would take 30 seconds to initiate any action whether that be opening an app or just clicking on something.
The CPU was idling at around 95% all the time and the memory was much the same with occasional spikes driving use up to 100%. There were no additional apps or programs open.

I have cleaned the disc permissions to no avail, I have tried to reinstall OSX Yosemite without a disk erase. After 24 hours of slow installation I am left with a half booted MacBook which emits a chime every minute. The screen is going crazy with several pixilated lines moving through. This leads me to believe there may now be a serious hardware fault.

The hard drive is only 30% full.

Has anybody got any suggestions on where to from here and other things to try?

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