Computer Freezing a computer fault ?

I was called out a week or so ago to a customer who had previously taken her computer to a so called expert who advised her that the reason behind her computer problems [computer would lock up after a minute or so after booting or under stress conditions] was due to heat and that she had fan problems and suggested her computer needed replacing or along those lines

within a few minutes of investigation i noticed that infact the computer was operating fine, no evidence of fan failure or noisy bearings, HD seemed to be fine with no corruption neither was the computer freezing, XP reported no software problems nor hardware problems, my suspicions then moved from software to a possible hardware fault, as the computer was only a few years old the bios offered the facility to show realtime voltage and temps, once again the temps were fine and that associated with a 478 celeron, voltages seemed a bit low but hardly under the ATX thresholds, now to eliminate any further problems i tested the ram within a dos environment and it came back clear so i then went to stress test hardware components within xp and bingo, as soon as cpu usage hit 100% the computer locked up, i tried again and it locked up immediately

To finish this article a new PSU and an hour later the computer was operating stable, she was charged 50% less than her previous quote, it always helps to get a second opinion and unfortunately the likes of PC world give PC repair a very expensive name