Deleted hash files; can't login anymore! I've deleted the two hash files in the folder /private/var/db/shadow/hash/, corresponding to my login account. Now, I cannot login, and don't have any other account on my Mac with sudo permissions.

Is there a way in which I can reset my password? If not, will it be possible to access data belonging to this account? My other accounts do not have permissions to these folders.
You can boot into the terminal by holding Command + S at startup. You could create a new user via command line this way. Here is a tutorial. Another option is to insert the installation disc and reinstall the Mac OS X.