I just bought a monitor for a relative's computer (Intel 82915G chipset) which should produce 1600x900. Though the current card can produce 1600x1200, there's no way (that I know of) to force it to produce 1600x900.
Assuming buying a card would be a solution, how would one find a cheap video card that can do 1600x900? They don't seem to list the modes in most ads.
If I'm missing something in Windows, please let me know, but I've looked around quite a bit and tried many things (including unsupported resolutions, etc).