Can recover your data if its deleted or disappeared by virus attack.
Can recover your data if the windows or hard drive has crashed.
Please don't re-install windows if you want to recover data from the same hard drive.
Once you overwrite those sectors on the hard drive where your lost files were saved than no one can recover the data.
If you reinstall windows or save new data or download new stuff into the same hard drive. you are actually overwriting to your files which you want to recover. so the more you use the less chance to recover.