I have the setup listed in my signature and I tri-boot with Hardy, 32- & 64-bit, and WinXP Pro. I have used the on-board Realtek 8111B LAN card since building the machine and had no problems with it until today.
Though I rarely use Windows, I was there today and foolishly let XP "upgrade" my Realtek LAN driver. Since the upgrade, I am unable to connect to the internet through Win XP or 32-bit Hardy. I even "rolled-back" the driver update in Win XP; no joy. My 64-bit Hardy seems unaffected by the change. Gigabyte's driver CD sees its drivers in place. Windows sees the LAN card and sees no problems (except that it can't connect). Hardy 32-bit seems to see the card but also can't connect.