I have two Western Digital "Green Power" 1 TB hard drives in my system.  I recently swapped out the DVD burner in my system.  When I rebooted I no longer had one of the drives listed in My Computer (naturally, the main data drive which I hadn't backed up before I swapped DVD burners).  Looking at Disk Management I see one of the 1 TB drives, my system drive, my new DVD drive and an unallocated 32 MB disk.  Checking the properties of that disk it says it's using the same driver as the 1 TB drive that shows up but it only recognizes it as a 32 MB drive.  I did not change any of the cables on the hard drives initially, when this started happening I swapped SATA cables, SATA ports, etc., all of which did nothing - the second TB drive remains intact, the one I "lost" remains a 32 MB unallocated disk.
 
Anyone have any suggestions?

Try setting it back the way you had it. Did you do the swapping with the power on or off?

Power was off (I swapped an internal DVD burner, there really wasn't a choice).  I haven't tried swapping back in the original burner (which doesn't actually burn any more), I can give it a try, though.

Wow I hope someone else can chime in because this is weird.

Try booting without either DVD drive...
 
Also list your MB and OS, and whether your drives are sata or ide, and how they are set up in your BIOS

So you lost a little bit of storage space,big deal.
 
Seriously, that is a weird problem.
 
Maybe try clearing CMOS?

Okay, I've rebooted without any DVD burner, same problem.
 
I've got a  GIGABYTE GA-M68SM-S2 motherboard, 2 MB of DDR2 800 memory, I'm running Vista Home Premium (this is an HTCP). the 1 TB hard drives are SATA, I've also got an 80 GB IDE hard drive as the system drive and the DVD burner is a Samsung IDE burner.  When I initially put the burner in I had the jumper configured improperly so the PC wouldn't boot at all, once I set the jumper properly the machine booted but one of the 1 TB drives disappeared under Explorer but was available as a 32 MB raw volume under Disk Management.
 
The Bios does not list the SATA drives at all, it only lists IDE devices - is there someplace else I should be looking for it?

Yo, sounds like a windows issue. Go to device manager then right click your 'puter and do a 'scan for system changes' Maybe windows has picked up the new dvd burner and allocated it under the same mapping as the HDD (the right terminology escapes me but at least I think I know what I'm trying to say)

Get a partition recovery program.
Try to recover the lost partition.
The Bios should show SATA drives.

 
I had tried that, it would find the hard drive but insist that it's only a 32 MB drive.  I did manage to find the SATA drives listed in the BIOS, both are recognized as WD10EACS which is correct.  It appears to be some sort of Windows problem but I'm stumped trying to figure it out.  Hey, it's only a TB of lost storage  

You may have a defective SATA cable connection. It could be not properly connected or have broke when you handled it.
You may have connected the SATA cable to the RAID controller by mistake.

You could have forgot to connect the power cable to one of the drives.
Sorry you motherboard does not have a RAID controller.

only Logical Block Addressing comes to mind...you know,  back in the old FAT16 and FAT32 days....the FAT16 actually limited your capacity to 32gb, didn't it?
 
first of all. I would check the device setiings in the BIOS - see if block size is set to auto or if any of the sata settings differ between the two drives.  
 
second: examine the "32gb" drive - for jumpers.  Some jumper settings actually limit drive capacity.
 
third:  give the drive a quick format to ntfs using the windows disk manager

Boot a Linux LiveCD. See if it recognizes the full size of both drives.
Reinstall Windows eventually if it does.

Run Hard Drive diagnostics from the manufacturer.

Well, after working with Western Digital technical support we've decided the drive is defective and I'm replacing it under warranty.  Thanks for all the suggestions.

 
This livecd is quite good:
http://www.knoppix.org/
 
or try bartpe for bootable xp (if you have a legal copy of xp lying around)
 
http://www.nu2.nu/pebuilder/
 
Oh, have you tried system restore ?

Before I'd send the hard drive on a few week journey, I would try CHKDSK /R . http://kb.wisc.edu/helpdesk/page.php?id=5097
 
If that doesn't fix it, try the FIXBOOT, and FIXMBR commands also.
 
Here' a bootable CD thats has similar repairs tools on it. http://www.ubcd4win.com/contents.htm

Could the 32Mb be the size of the drive cache?
If so it sounds like the drive has died.

 
Heh, hadn't thought of that (although the cache size is 16 MB, so that's not it).  But after running Western Digital diagnostics, trying several different cables (power and data), trying several different ports, booting with a Linux live disk and trying it in another computer WD and I agree the drive is dead.  Generally Newegg has been pretty quick at RMAs for me so I hope to have a replacement installed next week.  Again, thanks for all the suggestions.