TL:DR; Search for files that do not contain specified words or phrases within the actual file.
Download Search For Files That Do Not Contain Text Software Shareware - Rating: 4.69
321Soft Data Recovery Express (FREE undelete utility) is a do-it-yourself and free data recovery solution for FAT and NTFS file systems. It designed to easily recover deleted files from various storage devices, and It is Completely Free!
Attribute Manager program is a practical tool to take control of file and folder attributes. It enables to modify conventional file attributes, such as read-only, hidden, system, encrypted compressed, temporary and date/time parameters.
XSearch is a free search tool that with more features that Windows Search didn't provided. It can search files on your computer in high speed. When searching for special words in files, you can specify the words option etc.