SeeKaeWai

Hi, I found this site using Google, and I've got a really simple question to ask. I'm just beginning to get into electronics and stuff, so I may be visiting this site regularly! First of all, I aquired this analogue multimeter, but I'm doubting it's accuracy. It doesn't seem to read the voltage of anything right. But then I noticed there's a quite large sized screw that you can adjust the needle with, so it probably (actually, I'm POSITIVE) it needs calibrating. The question is; HOW do I go about calibrating it? I'm thinking I'd just stick it in a wall outlet, and calibrate the AC to 120V, but then again, I have no idea if my outlet is really putting out 120V (is this right? I don't really know if there's any deviation from a 120V wall outlet, or if an outlet ALWAYS puts out exactly 120V.) I really need to know, since my computer's motherboard and GPU gave out recently, and I'm wondering if it's because of the power supply. I tried reading the 12V rail, and it read as around 11.25V (Which definately isn't normal, 12V rail should deviate +/-5% at most). But, again, I don't think that's right, as the multimeter requires calibrating. Anyone? Also, do you think the battery life would have any effect?