The screen resolution (1600x900 or whatever else) won't have any bearing on this scenario. It's the 'Custom DPI' settings that will influence this.

Access this from the Screen Resolution screen by clicking the link to 'Make text or other items larger or smaller'. There is a 'Set custom text size (DPI)' option that must be 100%, and this is where the 'XP Scaling' option is that Andrew mentioned.