Turn the computer on and as soon as you have turned it on (before you see the windows logo, it's to late if you do) start tapping the F8 key.
you should then get a black and white menu, on that menu select "safe mode" and press enter, this will load windows into safe mode, you will get a warning about being in safe mode, just OK it and don't worry that everything looks huge...
Once the computer has done booting into safe mode right click anywhere on your desktop and select properties, then on the window that comes up click on the settings tab and slide the screen resolution slider all the way to the left, click OK and then restart your computer normally.
Once it restarts everything will be large again, so again right click on the desktop, select properties and select the settings tab and now start moving the slider towards the right, I'd suggest trying 1024x768 first and click apply, from there you can keep going up a step at a time clicking apply each time until you find the resolution that fits your screen best.
If at any point you go too far and it goes out off range again simply press the escape key or wait 15seconds and it will go back to the previous setting.