Judging by the error messages, you entered the command wrong.
This message:
Code:
usage: chflags [-R [-H | -L | -P]] flags file ...
suggests that you entered the 'chflags ...' command without a file, then hit Return.
The subsequent command-line and message:
Code:
el-earthbournes-macbook-pro:~ ELENA$ /Volumes/WD\ Passport/.Trashes/501/x
-bash: /Volumes/WD Passport/.Trashes/501/x: is a directory
shows that you drag-n-dropped the name of the directory AFTER hitting Return, so the shell tries to interpret it as a command. Since a directory isn't a command, the shell responds with "is a directory".
If you're following the instruction on this web page:
http://support.apple.com/kb/HT1526
Read through the instructions very carefully BEFORE trying to perform the steps. Pay special attention at Step 1 where it says this:
Note: Type one space (not pictured) after nouchg in the line above, so that it ends in "nouchg ". Do not press Return yet. [red hilite added]
If you still can't get it to work, post again, and copy and paste the exact commands you entered, in full, and any messages that appeared. Precision is important, and details matter.
Also copy and paste the following command EXACTLY, then post its output:
Code:
sudo ls -alO "/Volumes/WD Passport/.Trashes/501/"