Windows 7: randomly disappearing slave drives

Hi. I've read the posts on this topic, and mine shares elements but differs. I have had a new machine built for me with an ASUS mother board and running Windows 7 Professional 64-bit. My previous one had Windows XP Professional and the adjustment has not been easy.

Using "My Computer/Computer Management/Storage/Disk Management"; the following always shows up:
Disk 0 Internal Main Drive C: 2TB with Windows 7 Professional
Disk 1 internal SATA slave drive E: 150GB (ex Dell machine HDD, partition removed and reformatted)
Disk 2 internal SATA slave drive F: 185GB (ex Sony machine HDD, partition removed and reformatted)
Disk 3 external USB back-up drive G: 2TB Western Digital My Book 1130

I have always been in the habit of shutting down my machine when it is not in use. This is primarily because I live in the country, and power bumps are quite common. I believe this is what killed my last machine.

THE PROBLEM:
Whenever I start the machine, Disks 1,2,3 always show up in Computer Management , but not always in Windows Explorer. I am usually missing at list one, and often two of the drives. It seems to change randomly. I re-start, and get a different configuration. About one in ten start-ups, all drives appear, and function normally.

I will try switching SATA drive cables. One poster suggested that the main drive needs to be either disk 1 or disk 2, and slave drives should be disk 3 & disk 4.

Anyone have any other thoughts?

PS I don't have my new machine specifics handy since I am wiorking from another machine. I'll update that tonight.

Thanks in advance....

Vic

Well, the journey is finally over. It was the WD backup drive that was the problem. It worked fine in the XP environment, but bogged everything down in the Windows 7 environment. I tried many hotfixes and other suggestions to no avail. When I finally opened the WD external drive using another XP machine, removed the Password Protection, and completely reformatted the drive, removing all WD software, the Windows 7 machine began behaving as it should.

Vic