Windows – How to turn off the battery meter on the Thinkpad T500

As a former Lenovo tech, I don't even need to look up that code - 4x4 beeps is the TPM on the system board. Unfortunately, on the T42's there is no easy way to reset that...clearing the CMOS /might/ work but I dunno.

There is the slight possibility it's just static - take the battery out of the machine, unplug everything, hold the power button for ~30 seconds, release, tap a few times, hold again, release. Plug the AC adapter back in and leave everything else out - this MAY fix the problem. If it doesn't, you can try opening the machine, pulling out the CMOS battery, and leaving it for an hour. If that doesn't work you're probably looking at a system board replacement.

(I have seen ONE instance where a bad stick of RAM was causing this so it's worth looking into but it's INCREDIBLY unlikely.)

This happens if the capacitors on the board are overcharged; it's either a safety mechanism (to prevent overvolting, some motherboards do this) or simply a malfunction from the extra electricity. The act of attemping to power on the machine without a power source drains the capacitors, and voila - functioning laptop. There can be a lot of causes for this - static electricity, ambient humidity, unstable/dirty power source, problems with the battery, or even a problem with the motherboard itself. It shouldn't happen with any regularity unless there's a component problem, or alternatively you make your living doing belly slides on shag carpeting.

Note that this can happen, not just on laptops, but on desktop PCs as well. Beyond that, it can happen to pretty much any sufficiently sophisticated modern electronic device, in theory. Laptops are just especially susceptible due to their design, so it's generally the only place you see this behavior.