I never had that problem. It is read when I start a browser, but even then I can rename it.
Things to try:
1. Boot into Safe Mode. Might work.
2. Boot into Linux. A disc or USB-stick is free to make. You'll find the file manager in Ubuntu, Mint or Zoring easy to use. Be sure to shutdown Windows before you boot into Linux. Hibernating is not enough! This surely works.
I'm attempting to rename my 'hosts' file (C:\Windows\System32\drivers\etc). I've successfully managed to swap 'hosts' files before (to suppress unwanted ads). I'm now getting "The action can't be completed because the file is open in system". I've tried (a) rebooting, (b) using 'Unlocker', (c) searching for file handles to kill in 'Process Explorer' (but none exist).