My motherboard is a Asrock K7S8XE with SiS 748 chipset and i have the same problem with win 7. I think the problem is in the South Bridge SiS 963L. Somebody help me Sorry for the bad english. First of all. You should really have started your own thread instead of hijacking this one. Anyway, I did a quick search and found that currently both AsRock and SIS DO NOT seem to have drivers for either Vista or Windows 7.
If at least Vista drivers were available you might have been able to try those. So I think you need to contact AsRock tech support and see if they are going to come up with the needed Win 7 drivers for you.
Jul 04, 2011 Help!! Driver Realtek RTL8201 10/100 Ethernet driver for windows 7. Nvidia Nforce 10 100 Mbps Ethernet Driver Windows Xp.