Go to start menu, click search button then click all files and folders, type the file name, size, file type or modification date with specifying the location
Go into control panel. Locate find file on computer and do a search for keyword related to the file. Or whatever name you used to identify the file. You can also do a search of your computer for the same and should be able to locate it.
To search for files on your hard drive on your computer, go click the "START" button on the bottom left of your screen. Then click on "seacrh", then click on "search files or folders". Enter your search terms.