Henry Clark , May 21, 2010; 11:34 a.m.
The old EZ flash will not damage your EOS 7D.
It won't work very well either. It relies on the body having a sensor to measure the light reflected off the surface of the film. Digital cameras don't have this sensor, so it will only work if you set the flash power manually on the Speedlite and manually set an appropriate ISO, aperture and shutter speed on the camera.
If you want to use an old flash the 299T has a reflected light sensor built in and at least gives you some automation.
Only the EX series speedlites work properly with the Digital bodies.