Random reboot

I think I've found the issue.

Two signs put me on the right track: once the PC rebooted while I was playing in the BIOS settings, hence Win7 was unlikely to be responsible.
Secondly, I noticed that tapping on the right side of the case (on a very specific spot) made the PC shutdown/start.

I've removed the front card that hosts 2 usb, some audio plugs, some leds and the power on/reset button and I noticed that the reset button has the tendency to short-circuit itself (resistence goes down not to 0 ohms, but to a few ohms, probably enough for the circuitry to pick up a reset signal and trigger a reboot).

I've hit the button to see if mechanically everything was in place and now it seems to work fine. In any case I've set Win7 to do nothing when the button is pressed (before the action was shutdown). So right now, the worst it can happen (if the button fails again) is that the pC wakes up by his own. In case, I can always try to replace the button somehow.

Thanks for all the support, really appreciated !

MaX.