I have recently built a PC for a friend, after the original system build, which included a 60GB primary SSD and a secondary 1TB HDD.
I kept getting blue screens of death and kernel power errors, after investigation it was revealed that a faulty power cable and insufficient thermal paste provided with the included heat sink was the cause.

This resolved the problem but after 3 months I received a phone call saying that the PC was not starting at the point of loading the operating system, with an NTLDR error.
I had an idea of the cause, and after the user removed the HDD the computer started up with no issues, then I asked him to power off and reattach the HDD, and this completely resolved the issue; beforehand even restarting would not fix it.

He does not have a surge protector and I thought that maybe some registry corruption had occurred due to a power surge, this might be a stupid answer though.

Any ideas to what occurred with the machine would be most appreciated. No other issues have been found since the initial fault. The PC uses Windows 7 Home Premium installed on the SSD.