The two things you haven't mentioned are RAM and the power supply- have you tried to verify either of those yet?
DMR
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Faulty RAM can do all sorts of strange things, so I wouldn't rule it out (especially given that you seem to have replaced almost all of the the other major components).
Also: this may be a long shot, but I know that at least a couple of models of laptops will start to exhibit symptoms (including locking up and/or not booting up properly) if either their main battery pack or the CMOS/motherboard battery are failing.
Unfortunately, I'm not very familiar with the Tecra laptops, so I can't say specifically what other components you might want to check.
DMR
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I really don't think the OP will still have the same computer now, this thread was last posted to on Jun 18th, 2005
Bob_180_Bob
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