Hi, hw23:

My suggestion would be not to use the standby or hibernate functions. These functions are notoriously unreliable for desktop machines.

Thanks for your answer. Since I am not using it as a server, I just want to save some energy by choosing standby. I have never seen that 2ndary drives are lost before with other computers. I have tried to search online for answers, but so far, no Vostro 420 was reported  with similar problems. Therefore, I am kind of afraid it is quite unique for my computer, there could be something wrong with motherboard. Anyway, do you have some explanation of what could be the reason?

Thanks again.

Yes, don't use standby or hibernate. That's my explanation and I'm sticking to it. :emotion-2:

Thanks. I just disabled sleep function for the HDs. Let's see if the problem will be solved. I found I was using AHCI instead of ATA in my sata drive controls in the BIOS. I am not sure this could be a reason.

Anyway, thanks