There are several ways to search for files under Windows 7. The simple way is to use the Search bar from File Explorer. You can find the search bar in the upper right corner of any window. To use the search function, just type the filename in the search bar and press Enter. The computer will search for your file in all the folders that are displayed.
Another way to search for a file is by installing a program that is specially designed for this job. You can use Software Informer's database in order to find an application that suits you.