I have a 'MyBook' 1-Terabyte external drive, mfgr. Western Digital, USB connected, about 2 yrs old, for
Monthly backups. To backup, I simply create a dated folder (like 'Bkup_20110801'), and manually copy my doc- & pic-folders from my PC into that dated folder.

The drive now contains about 22 dated backups, and a *lot* of files, and is a bit over 1/2 full.

But this last time, the newly backed-up docs would vanish before almost my eyes! The Copy completes normally, and I can see the copied subfolders within the dated folder. But when I pop out of the folder and go back in, the subfolders are gone.

What is wrong? Does the external drive have a limit on the number of files or folders it can hold? Note, the file system is FAT32, my Windows OS is Vista, and the PC manufacturer is Dell. I do regular maintenance and virus/malware scans on my PC (using AVAST, Ad-Aware and other tools). None of the backed-up files are >2G in size.

I am now running a Defrag on the external drive in hopes that this might solve the problem. The defrag has been running about about 24 hours now. It probably has a long way to go. But I suspect this is clutching at straw.

Please help me save my backups. Thanks.

I have had to tear apart at least 3 of those external hard drives to save client data. The little circuit board in those devices seems to be the failing point. If you open the drive up and slave the hard drive you'll likely see your data.

What kind of cable are you using to get from the computer to the external hard drive ?

Mystery solved, sort of. After the drive Defrag, the copied folders appeared again. Then disappeared. After some fiddling I found that the Copy had for some reason assigned them the 'Hidden' attribute (and the Backup folder was set not to show Hidden subfolders). This had never happened before, and I am still unsure why -- maybe a circuit board glitch. Now at least I know what to look for, and how to fix it! Thanks for your hints.