well as John Mitchell pointed out the ren command syntax found here does not allow the path of the filename as part of the second parameter.
however, the MOVE command syntax found here will do what you want, i think, and it does allow the full path.
move c:\Data\contents.txt c:\Data\contents44.txt
Lowell
--
help us help you! If you post a question, make sure you include a CREATE TABLE... statement and INSERT INTO... statement into that table to give the volunteers here representative data. with your description of the problem, we can provide a tested, verifiable solution to your question! asking the question the right way gets you a tested answer the fastest way possible!