well for a start you need vista to SHOW hidden files. Of course this is still not of much use since you cant remember the filename but a start nonetheless.
Click START then CONTROL PANEL and go to APPEARENCE AND PERSONALIZATION then under the FOLDER OPTIONS click on SHOW HIDDEN FILES
A window will open up and you need to check the option to show hidden files. Also uncheck "hide extensions for known filetypes"
"Hide protected operating system files" is checked by default and i wouldnt recommend unchecking that option for obvious reasons.
Click APPLY when finished
Now the rest is up to you, click start and type windows explorer and enter and away you go to find your now revealed hidden file, whatever its called :)