I have Windows XP SP3. I was copying files from my ADATA 500 GB external hard disk (via USB 2.0) when a "Delayed Write Failed" error came up.
Now I am unable to access it and it gives the error:
The file or directory is corrupted and unreadable
Right-click on the drive in My Computer, select Properties, and under the Tools tab, click Check Now.... Set the Automatically fix file system errors check box, then click Start.
This will scan the hard drive for errors. If the check needs to be scheduled for the next boot, do so and restart the computer, leaving the drive plugged in; the system will perform the check on the next boot. If any errors are detected (which it should),
For more information on how to check for errors in a disk file system, see http://support.microsoft.com/kb/315265.
Edit: Since you indicated that
If there are not important files on the drive you can just format it. Formatting may make it normal to use again.
also you can try chkdsk for the parititon, as the error message "The file or directory is corrupted and unreadable" is mainly caused by file system error:
3 Continue to type chkdsk /f g: and press Enter. G is the drive letter of the problem partition and it can be F or other letter on your computer. Type Y and hit Enter and restart computer to resume disk check if you get the message "Chkdsk cannot run because the volume is in use by another process. Would you like to schedule this volume to be checked the next time the system restarts? "
Note that, even chkdsk may cause data loss, thus you need to retrieve data first if files on the disk are impostant to you.