Network connection vanished after windows 7 service 1 update

Hi maybe this problems have been posted before....

I recently bought a new PC and after updating to service pack 1 for windows 7 professional the ethernet network just disappears.
it says no connections are available then when i click trouble shoot.
The problem that it detects is that "windows did not detect a properly installed network adapter if you have a network adapter you will need to reinstall the driver"
I then use my original instal disk that came with my asrock motherboard and instals the realtek driver but it says " realtek network controller was not found if deep sleep mode is enabled please plug the cable"

i tried restoring the system to a few days ago and the ethernet works again however when i tried to instal the update the 2nd time this problem appeared again...

can someone help thanks

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