Hey Vu,
RE: One thing I have run into on dual boot boxen is that Windows "reboot" does not clear everything in the NIC which causes Linux to fail the setup. If you've been in the Windows side, do a complete shutdown and cold-start into Linux. This clears whatever trash Windows is leaving behind on a reboot.
Sounds funny but why not. I have Win XP Pro as well as Suse 9.0 on my system and although there were a few initial headaches the Nic worked fine. If the problem persists you may have to try Suse Support again. Because it must be something you are doing in install otherwise it would not work under Windows either. As to a second Nic almost any 10/100 card should work. It is not necessary to spend $50 on a 3 com or a linksys, even a lowly DLink for $10 should work. Donald