keep losing HDD's using windows 7

You may be using the SATA connectors in a non-optimal order.

Also, get the drive diagnostic software for each of your drives from the relevant vendors and run the tests. A drive on its way to failure may be borking the whole system.

Did the Win 7 upgrade advisor say that the system was fully compatible with 7? Do you need to update any of the drivers (esp. board and controller drivers)?

Westeren Digital Data Life Guard Diagnostics is available here

http://support.wdc.com/product/download.asp?groupid=502&lang=en

Seatools for Seagate is available here

http://www.seagate.com/ww/v/index.jsp?locale=en-US&name=seatooldreg&vgnextoid=480bd20cacdec010VgnVCM100000dd04090aRCRD

And Samsung Utility ES Tool is available here

http://www.samsung.com/global/business/hdd/support/utilities/Support_DiskManager.html

As stated above download these 3 utilities and test the drive that it works with to confirm correct Function. If a Drive is on it's way to [b]Silicon Heaven[/b] it can cause screwy problems like the one you have described here.

Also check your M'Board Manual for the correct Placement of SATA Connectors on the M'Board. Some ASUS M'Boards have a paired set of SATA Connectors to use as a RAID Array and when you connect different drives to these they can cause them to disappear.

Also check your BIOS to make sure that the SATA Setting isn't set to RAID as this can cause a SATA Drive to disappear as it's being used in some sort of RAID Array and is no bigger than the smallest drive in that Array.

If the HDD fails the test remove it and retest in another computer. If it still fails the test it's gone or is on it's way to [b]Silicon Heaven[/b] but if it passes the Second Test the Power Supply, Data Lead or M'Board in your computer needs attention so that the computer can work correctly.

If you no longer have your M'Board manual you can download it from ASUS here

http://support.asus.com/download/download.aspx?SLanguage=en-us

Just enter the Model Number and select Manual from the Drop Down list below the Model Number and then click on Search.

If your ASUS M'Board is a [b]Special[/b] made for a company like HP, Dell or so on then you need to go to that Companies Web Site for the M'Board/System Manual as ASUS doesn't support these Specials.

Col
[i]edited for clarity I hope.[/i] ;)

is that after the power failure or before

if you can see them in another system after the fact

then the power failure took out your MB disk controller

Since the Power Failure?

The Power Failure could have damaged the M'Board/HDD.

Or it could just as easily be a Wrong Setting in the BIOS so have you tried returning the BIOS to Performance Defaults?

Anyway as ASUS doesn't provide any Windows 7 Drivers for this M'Board what makes you think that it works with Windows 7? If there is a Incompatible Chip Set with 7 the M'Board isn't going to work and missing Drives could just be one example of the problems encountered with using this M'Board with Windows 7.

Col