do i need the realtek ethernet controller driver?
I agree with ksiemb, slightly vague question.
Assuming you mean "Windows 7 installed a driver for my RealTek ethernet controller, should I just leave it alone or find the correct driver from RealTek?"
I would recommend that you download the latest driver from RealTek for your ethernet controller. The driver Windows 7 installed is probably either an older version or a generic driver.
You could also check your motherboard manufacturer's website to see if they have posted the latest driver for the ethernet controller for your board for Windows 7.