Label Object font size is larger than it must be!

I created a test indicator which draws a Label Object with "Arial" font name and a font size of 10. I tested the same code on four different computer/Windows 7s. The strange thing is that the size of the text of the label on one of the computers is (much) larger than the rest (the text looks the same on three computers). I reinstalled the "Arial" font on that computer with no success. I uninstalled and reinstalled MT4 platform with no success. I tried to reset Windows 7 fonts, but it also didn't work. Does anybody know what the problem is, and how I can fix it?