Cannot Enter Windows Menu After Replace RAM

Hi Experts,
I have replaced RAM into another slot, then I couldn't enter window's menu.
There is a message:
PXE-E61 : media test failure check cable.
PXE-MOF: exiting NVIDIA boot agent.
Reboot and select proper boot device Or insert boot media in selected boot device and press a key.
Need your solution.
Thanks a lot..
