Thanks for your help, fortunately I didn't have to go that far. In this case it wasn't an issue of process association.
I thought I'd share how the problem was solved though, in case it happens to anyone else in the future. I downloaded a program called "hijackthis" which could not delete it conventionally either, but then while tinkering with it I found a feature of hijackthis that can delete any file upon restart. I had to do this 6 times (as the cassandra files were duplicating themselves) but this completely deleted alll of them from the computer. Thanks again for your help.
Dan Hatch
Zetch131411@hotmail.com