Did you install the manufacturer's graphics driver for Windows 7?
It sounds like it's using the default basic Microsoft driver which loads by default if the manufacturer's driver is missing, and the basic Microsoft driver cannot access the full range of resolutions.
You need to install the proper graphics driver. Where you download it from depends on whether it's an "on board" graphics chip or a separate graphics card which fit's in a PCI or PCI-Express slot.
If it's the former and the PC was factory-built, download driver from your PC or laptop maker's website, or from the motherboard maker's website if the PC was not factory-built.
If it's the latter, download driver from the card manufacturer's website.