First occasion. Earlier this year, a friend's DELL PC went completely dead - small indicator light on motherboard lit and fans OK, but no beeps, to screen signal, no HDD activity. Disconnected all add-one, except one DIMM (including Keyboard & Mouse). Still nothing. Took out fianl DIMM - still nothing. Put it all back together - still nothing. 2 days later, suddenly working a if nothng ever wrong.
Second occasion, step-son insert additional DIMM, but used DDR2 when needed DDR. Computer completely dead. Removing DIMM made no difference (damage done?). Computer still dead - no beeps or anything. He did all the same checks - still nothing. 2 day's later suddenly PC comes back to life and no further problems a month later.
Today, another friend mentined that his HP PC had been dead for at least 2 days. Previous to that, for a couple of days PC stopping suddenly after short period of life, but able to re-start. Also no significant Internet (but that could be becuase of ISP problems). Took at look. No signal to monitor and no indication of HDD activity. No beeeps (except when I removed all the memory when I got a series of short beeps). Put it back together but still nothing. 6 hours later, PC suddenly comes back to life although mouse not working and very slow activity.
Am I missing something? My friends and family depend on me to sort out their PC problems and that's 3 times I've declared a motherboard knackered only to find it come back to life inexplicably.
Only things they have in common: All using Windows XP, all PC's about 5 years old, and none of them have any surge protection.
Yes, I thought of the PSU, but the fact that 2 of the three have since shown no probrlems, in two cases over 6 months and 2 months respectively, would belie that fact. CPU over- heating I would also have ruled out for the same reason.
In fact, with the 1st PC, I now hae ths onm a test bench and have been throwing all sorts of bad practice at it but it still keeps on going.