There are a few different options available to you if you are unfortunate enough to loose some of your data depending on what hardware you have and what level access you have on your computer. Windows 7 has the option to restore previous versions (although this may not be enabled by default). Previous versions are either backup copies—copies of files and folders that you back up by using the Back Up Files wizard, or shadow copies—copies of files and folders that Windows automatically saves as part of a restore point (Shadow copies can be copies of files on your computer or shared files on a computer on a network.). You can use previous versions of files to restore files that you accidentally modified or deleted, or that were damaged. Depending on the type of file or folder, you can open, save to a different location, or restore a previous version. To learn more about this, click this link.