System not "sleeping" properly

[Hells_Fury]

Of late, when i put my system in standby mode, the system goes into standby properly, but the CPU fan still spins at full speed. Any pointers as to why this is happening?
This started happening recently itself, earlier the entire system used to go into standby...

 

[Kiran.dks]

I doubt that the fan running is a Power supply fan and not CPU fan. Just open the cabinet in stand-by mode and check which is running.

 

[Hells_Fury]

I already checked, its the CPU fan. Like I said, this wasnt happening earlier. Started recently.