HashTab is a Windows shell extension which adds a tab called "File Hashes" to the Windows Explorer file properties. The tab contains the MD5, SHA1 and CRC-32 file hashes. These are common hashes that are used to verify the integrity and authenticity of files.
Many download sites list the MD5 hash along with the download link. The HashTab makes it very simple for Windows users to check these hashes on any file on the system without using external tools. The screenshot to the right shows an example.