Vista - Need help with Ethernet controller in Vista and Windows 7

Hello all
I have a ECS A740-M motherboard with AMD Athlon 64. I have installed Vista Ultimate x64 version in HDD 1 and Windows 7 Beta x64. Everything was working fine and all of a sudded a couple of days ago, the computer wouldnt boot Vista or Windows 7. It starts to boot and hangs. In safe mode, I found the Ethernet controller Atherros L1 gigabit Lan was the problem. I uninstalled it and on booting, it booted up normally without the Ethernet connection. On installing the driver, again both wont boot.
I reinstalled Windows 7 and still there is no change in results.

I have SP1 installed for Vista and I cannot even uninstall SP1 as it is not displayed in installed updates under Add remove program. Tried all known ways to uninstall SP1 and failed.

The lan connector is onboard. I tried unistalling the Atheros Ethernet connector and added PCI netgear Ethernet controller and I could not install it as i could not find drivers for it.

Any help is greatly appreciated.