Since Windows 7 is still in Beta stage no Motherboard manufacturers, manufacturers of add -on cards, other devices such as Modems,Printers, scanners, WebCams, etc etc which have become part of Modern Desktop computers "peripherals" , and computer manufacturers themselves will create drivers only after they get the Win 7 RC. Some big manufacturers have started to make some software for the Win Beta 7 but their number is small [ Example Check this NVidai site: NVIDIA Graphics Supercharge Microsoft Windows 7]
One rule of thumb I use in selecting MoBo or devices when building PCs is to see if they are VISTA compatible. I had no problem using that rule in installing the Win 7 Beta in any of the PCs I have built.
Hope this answers your questions in full.