Yes they keep your files. No, past denials don't affect future applications.
I think they can effect you if you apply before you are allowed to re-apply. I have heard that in some denial cases applicants are not allowed to apply for another 5 years.
how about withdrawn applications. Do they try to pursue a withdrawn application for denial. The reason i asked is in my case I have withdrawn my application still no acknowledgment yet and mean while I was asked to pay some back taxes for 2007 which I promptly paid. could that be a reason for waiting for not sending acknowledgment?
have you been denied ?