Use AutoCAD's Rename command to rename the file name of blocks. This is a great tool if you have an error in the name of the block or you just want to change it to something more manageable. I don’t know how old this command is, but it's new to me!
Notes from Cadalyst tip reviewer R.K. McSwain: Although the Rename command goes way back, probably more than 25 years ago, it's probably this reason that a lot of current day AutoCAD users may not even know it's there. You can use it to not only rename blocks, but textstyles, dimstyles, tablestyles, views, and many other objects.