appreciate help on how to unlock files and directories.
once trying to clik into a directory got a message: no access to xxxx

What indication do you have the file or folder is locked? I know of no way to lock a file or folder. You could have received that error message if a file or folder has been deleted... it sometimes will still show in Windows Explorer after being deleted. Then when you try to access it, you will get that message. Click on View and Refresh and tell me if that locked file or folder is still there.

well, files and directories are stil on h/d. however, there is no access to some of the directories. it seems that these are locked by the system.

You cannot lock file or directories (folders) with just Window XP... it isn't possible. However, it may be possible using some 3rd party application. Are you running any such app(s)? Are we talking while you have Windows Explorer open?