Take the 2-minute tour ×  My Windows 7 Home Premium 64 on an i7
940 CPU Gigabyte motherboard sleeps suddenly while in use
(typing or clicking mouse) since I installed SP1.  Sometimes it
does not boot up when first turned on and I have to press reset
to boot up. It worked fine before in balanced power mode, I did
not change any settings before or after installing SP1.
share|improve this question  2 Answers 2  It might be that the
computer is overheating (you haven't over-clocked it by any
chance?).  Good products for keeping an eye on the temperature
are the general-purpose SpeedFan and the GPU-oriented GPU-Z.
Something else to try :  Disconnect all cables and devices to
the computer and power off. Disconnect the computer from the
mains and leave it off for at least 30 minutes. Then turn it on
and reconnect the minimum number of devices you need. If the
power is through an over-crowded or old power strip (surge
suppressor), you might want to try connecting it directly to the
wall outlet, at least initially.