Hide file URL and allow a rmb 'Save As' rather than forced download on LMB?

[techbinge]

I've got some paid digital files that I  need to serve up while hiding the file URL. That part is pretty much taken care of. However, because IE7 / 8 throw such a fuss about forced download files (i.e. the popup like blocker, warnings, etc), I need to offer a 'Save As' alternative to saving these paid files. No idea how to do this w/ PHP, and still obscure the file URL.

 

Any help would be appreciated!

 

-Tyler