Freezing Desktop Problem

HDD failed in neighbour's PC (A8N-Sli SE) so I treated it to an SSD and Windows 8 (64bit). Setup went fine, whole thing steady as a rock. Installed on his desk, froze completely within minutes. Took it back, continued to freeze. Reinstalled W8 32bit, again all perfect. Took it back, froze again. Only difference in situation was PS2 mouse/keyboard, so took the whole lot back to workbench where it works perfectly. Only difference left is the power cable/mains supply. It runs cool as a cucumber, CPU 35 and Mobo 32. Rail voltages spot on, Memtest 86 run for hours, no errors. Couldn't be a fault on his Mains supply, surely? Any thoughts?