It's up to you to remove sensitive or personal data from your computer before taking it to a free computer recycling site.

The free recycling sites are part of the E-Cycle Washington program and this program does not guarantee the security of confidential data stored in the electronic products they collect.

Simply formatting your drive or deleting files doesn't destroy data. Many software programs, though, can do this for you. TechSoup has articles explaining how to destroy your data:

One local E-Cycle Washington recycling site, AllShred, offers hard drive destruction for a small fee.