Well it depends on how you encrypted them. Was it a third party tool? Or did you use the built in windows Encrypted File Sytem to do it?
If the EFS, as Dzomlija indicated, that's kind of the point of the encrypted file system. The files can ONLY be decrypted on the machine with the same user account that created them. Not just the user name and password, the /actual/ account and it's associated credentials. So if the drive is removed it cannot be decrypted anywhere else, even if they got your user name and password and created a new account.
If you had exported your credentials or made an encryption recovery disk or assigned a differnet user (that still exists) as a data recovery agent then there might be a chance but if not, and you reformatted your drive that old user account is now gone forever and so is the data