That is of course your prerogative. I will say however, the fact that you used it with an older build means it also has some miles on it. A unit that is of questionable quality that has already been around the block and is then used with what is probably a higher demand graphics card than what was previously used, is one of the prime scenarios we see here with threads that result in power supplies being the problem. Still, there is always some room for doubt.
I'd test the unit to at least get a basic idea of it's condition. It won't tell you whether at that 4hr mark something isn't wrong, but it might show some indicators.
https://www.youtube.com/watch?v=ac7YMUcMjbw
As I said, if the card isn't at fault, the PSU probably is. Clearly though there could be issues with the older drive, the GPU card drivers or the OS itself. Might be a good idea to do a clean driver install and test the drive as outlined above.
Clean GPU card driver install: http://www.tomshardware.com/faq/id-2767677/clean-graphics-driver-install-windows.html