and....?

"We got you, some bits of your hard drive have changed"

"yeah. and?"

"did you write files to that bit of your hard drive?"

"sure, that's what hard drives are for"

"so why aren't they there now?"

"because I wiped them with heidi erasor"

"why would you do a thing like that?"

"because I was going though US customs and its now our company policy to do so in case they (for example) decide to make a "backup copy" of all our valuable customer data"

"we wouldn't do that"

"so where did you get THAT backup from then?"