decrypt file after formatting xp

i've encrypt some files in a drive. my os win xp sp2. i've to reinstall my os. i've changed my user name and password. now i cann't decrypt those files. please help me............

You should not Delete or Rename a User's account from which will want to Recover the Encrypted Files. You will not be able to de-crypt the files using the steps outlined above. As you have formatted XP i don't think so you can recover.

Refer to this Microsoft Guide: How to remove file or folder encryption in Windows XP

Hope this will help to resolve problem.