Solution or Workaround
Why do I get the following error when trying to BUILD a coverage from ArcToolbox?
ArcToolbox Warning (Window title)
(Yellow Triangle with '!')
Unable to establish a WRITE lock on the following data:
Another program, such as ArcMap or ArcCatalog has a write lock on the data trying to be built in ArcToolbox.
If ArcMap is accessing the coverage in one of the layers, remove the coverage from ArcMap by selecting it and right clicking on it in the Table of Contents and choosing REMOVE.
Even if you have released the lock on the data in the other program, it may still take a minute or two for your ArcToolBox Build tool to register the lock's release.
If the above solution does not seem to work, save any changes in the program where the coverage could be accessed, then quit out of the program and try the BUILD in ArcCatalog.