Changing my keyboard question

[rocketman]

I have some time to change my keyboard on my T42, the Chineese version to the Thai version. I removed the battery and am trying to remove the screws but my philips screwdrivers aren't catching, I've tried a few sizes but they seem to be either too small or too large. Am I supposed to use a particular size or type of screwdriver? I can try harder but I'm afraid to put too much pressure on the underside of the case.