Could be a trace on the motherboard that opens when the board bows under its
own weight, or a power supply lead that has a bad connector. That connector
might work when it's oriented a certain direction, but not another where
gravity can tug the wires leading to it into a different shape or angle.
Investigate the power supply first before you go after the mainboard.

-----Original Message-----
From: Personal Computer Hardware discussion List
[mailto:[log in to unmask]]On Behalf Of Russ Cox
Sent: Saturday, January 12, 2008 1:02 PM
To: [log in to unmask]
Subject: [PCBUILD] lazy computer!!


This is way wierd to me.  I have an HP7955, 16.GHz P4, 512 MB RAM running
Win XP Home.  It has an NVIDIA video card, no other expansion cards.
It locks up during startup.  No response to mouse or keyboard and the time
doesn not change. But when I set on its side, it works just fine almost
every time.
I have:
replaced memory several times, using different DIMM sockets
replaced the hard drive
removed the extra expansion cards - modem, IEEE1394 card
swapped the video card for another similar card and updated the video driver
all connectors are tight

It has on occasion, locked up during boot, during startup, even in safe
mode. It sometimes fails to boot at all. HDD LED comes on but nothing
starts.
I have removed everything I can from the startup list, leaving only those
programs that look like basic Win system programs.

The most consistent item is that it works reliably when on its side, most
often locks up when upright.  Nothing is moving that I can see.
My best guess now is that there must be some stress on the motherboard that
changes when it's on its side.
I have been struggling with this machine for several weeks now, and can
think of nothing else to try. Othe than replacing the whole machine.
Any other ideas?

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