Windows 7 not going to sleep mode

[sourishzzz1234]

I have Windows 7 installed in C:\ and Fedora 12 on different partition...i installed the fedora later so the boor loader is grub.....but after installing Fedora i have noticed that though my PC worked fine with both the OSs but in Windows 7,sleep mode doesnt work....

on pressing the sleep mode the screen goes off but after some seconds returns to normal screen again..i tried with poweroff3.0 same thing happened...when i tried standby from there it said "File not found"

i turned off the wake up from Ethernet and mouse option off from device manager but in vain...

Please give me a solution for this........