My computer hard drive keeps trying to park

[CompileMonkey]

Hello,
my harddrive keeps trying to park and I lose the logical drives out of the computer listing. But my bios sees the drive in the boot up listing. And it does temporarily appear upon intiatly entry into the os. What could be the cause and how to fix?
Win7, wd500 not even a year old

 

[house70]

If it happens after a period of inactivity, it could be that the hard disk is set to "sleep" after a certain amount of time. you can disable that in Power Management> advanced.