Windows network Disconnects randomly

My laptop's Windows Network disconnects randomly with "Media Disconnected" message in windows xp, Most of the time its when the system is idle for some time..Simple way to fix this disconnect and Connect back the Network cable to Ethernet slot, It will immediately connects..
Struggled lot to find the root cause..but no luck .
Today I found a probable root cause , It seems Ethernet device Power management option seems to culprit , It seems this option will cut off the power supply to ethernet device , if network is idle for sometime.. After disabling it it seems I have not seen the error back.

To disable it My computer -> manage-> network adapter -> properties