I am using Archicad13 64 in Windows7 64 and when I zoom my drawing to ACTUAL SIZE it looks little than the actual size. I compare this placing an engineer's scale over my LCD monitor and it looks small.
If I run Archicad13 32 bits over "Xp mode 32 bits " in windows 64 the same drawing looks perfert in actual size, even placing an engineer's scale.
Not sure if this is helpful, but if you go to the "Display Properties" (right click on the Desktop and click on Properties), then the Settings tab. CLick on the Advanced button and under the General Tab will be a setting for the screen DPI setting. Try that at different DPI's and see if you get different results.
