Windows 7 - HDMI for monitor

I just purchased a new gateway desktop/monitor. It came supplied with 3 moniter cables, vga, dvi and hdmi. The only way it works is with the vga cable. With the other two the moniter reads no signal. I have contacted gateway numerous times and they have not been able to help. Any thoughts? Thanks,

Welcome to SF!

Have you tried updating your drivers for your video card/monitor?

gateway sent me a link to download a driver. when i tried my system said it did not support the driver

Try finding the driver yourself. Go to the manufacturer's site, and navigate to the Drivers section. Then choose your card.

This is a shot in the dark.
If the VGA port is in a different location than the DVI and HDMI ports on the back of your computer, and the DVI and HDMI ports are located next to each, then your computer probably has both an onboard video adapter(VGA) that's built into the MB, and also a dedicated video card(DVI & HDMI).
If so, then the onboard video adapter may be configured as the primary display device in BIOS. If that's the case, then configure the video card as the primary device, and see if that helps.
(NOTE: Possible designations for the video card in BIOS may be either PCI-E x 16 or PCI-E x 1, depending on which MB slot the video card is inserted in.)

But if all of the video ports are lined up next to each other, then they're probably all on a video card, and different drivers may be the solution, as suggested by Jonathan.