Realtek RTL8168B/8111B Family PCI-E Gigabit Ethernet NIC.
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Realtek and down load this-> Win7 and WinServer 2008 R2 Driver7.0342010/12/22
Use device manager to force a driver update.
Expand network adapters, right click the problem adapter and choose update driver software, then Browse my computer, then Let me Pick, then have disk, then browse, browse to the folder where you downloaded and extracted (if necessary) the driver noted above.
If that dosen't help try this
type ncpa.cpl into the search box and hit enter
right click your adapter and choose properties
click the configure button
choose the advanced tab
look for something called speed and duplex (may be worded slightly differently)
select it then in the right column select the drop down arrow and choose 10Mbps/Half
OK your way back out of there and reboot
If that seems to work for you then start experimenting with different settings, because your card/driver is having a problem auto negotiating link speed and duplex settings with your router.
Ideally a setting of 1000 full (never half with Gig Ethernet) is what you would want, so change to 100 half and reboot, then 100 full and reboot, etc.
Keep us posted.