Checksum Verify is an easy-to-use program that allows you to create and verify checksum files.
Checksums are values that are based on the contents of a file, so if the file changes, even by just a single bit, then you'll get a very different checksum result. And so you could use a checksum with a file that you've backed up to CD, perhaps, to confirm that the backup hasn't deteriorated over time. Or you might verify someone else's checksum for their program's download, to confirm that no-one else has tampered with it, perhaps to add malware.
Checksum Verify can verify all the main checksum file types: .sfv, .sha1, .par2 and .md5. And it can create .sfv, .sha1 and .md5 files, depending on your needs.
Whatever you're doing, it remains generally easy to use - just choose the option you need from CheckSum Verify's task menu and follow the instructions.
And multithreading support should improve performance, although the default setting of 8 threads may be a little too high. If you find the program works a little too slowly for you, click Settings, reduce the number of threads to 2 and see if that makes any difference.