More info from another forum thread:
"Does your laptop support Dual-Link DVI?
That's a requirement to reach the resolution of the 30" Apple display. If your PC laptop doesn't have onboard dual-link DVI, the monitor can't be expected to work. If you plugged it into a VGA port on your laptop because your laptop doesn't have DVI, it won't work. Your VGA-DVI adapter might be single-link. I don't think VGA, an analog standard, has the capability to drive it."
"Can I use a DVI-D to HDMI cable? Will that work?
No. The 30" needs dual-link DVI. HDMI only carries single-link DVI signals."