Connecting Ethernet cables causes dsl and internet lights on my modem to go off

Here is my strange problem:
After reinstalling windows 7 on my old pc, I cannot use my Ethernet cable to connect to internet.
I have a dlink dsl2730u modem. When I connect the Ethernet cable to my pc, suddenly the internet and dsl lights on my modem turn off. As soon as I disconnect the Ethernet cable, the dsl light starts blinking again.
I was able to connect to internet using Ethernet cable before I reinstalled windows 7.
I used the very same cable and connected my laptop to my modem and there was no problem. (so, I concluded that the cable is fine)
Also, I downloaded and installed the driver for my network adapter both from Realtek website and my motherboard manufacturer (msi) webpage. But still there was no progress. Can anyone help me with this issue please?
P. S: sorry for my bad English.