Disk Redactor

Disk Redactor is a WIPE utility that lets you securely erase any old (deleted) files and prevent them from being recovered. All your private sensitive insecurely erased information will be wiped from free unused space on your drives to ensure complete data destruction. This is necessary because when you delete a file, it is not gone forever, and any file removed from the Recycle Bin can be easily recovered! The Windows delete function does not clear the space where the deleted file has been located but only marks an entry in the directory (folder) as deleted. All data and information about the file still remains on the disk and can be restored.

http://www.cezeo.com/products/disk-redactor/

Anti-Virus Test File

A number of anti-virus researchers have worked together to produce a file that their (and many other) products "detect" as if it were a virus. It is safe to pass around, because it is not a virus, and does not include any fragments of viral code. Most products react to it as if it were a virus (though they typically report it with an obvious name, such as "EICAR-AV-Test").

http://www.eicar.org/anti_virus_test_file.htm