I'm a relative newbie at assembly language programming also, so I'm not going to try to answer your main question, but I'm really curious as to why you think assembly has "lower level access" than any other programming language, and what that exactly means.

seeing as all compiled languages all end up running as machine code which can be directly translated into assembly language, you should be able to do most things with most languages, writing assembly just gives you a finer level of control. 

anyway, just thoughts.

*Caveat* I am not an Assembly guru by any stretch of the imagination.
From what I know you are correct that Assembly doesn't use file handles it uses memory addresses instead (I think).  You could definitely write an Assembly program that accessed a locked file using it's memory address.  Although you might be limited in what you could do with it.

So.. I'm not a windows kernel hacker, but here is some speculation.  My guess would be that the ideal way to get to the things that you want is not assembly, but instead dll injection.  If you want to delete locked files, process explorer can probably help you.  If you want to scrape program memory, a debugger or such can be your best friend.  So I guess the real question is, what is your goal.  A file handle is basically just a view into the file that the operating system helps you keep track of so that you aren't doing a lot of other work that the operating system is already doing for you.  Files aren't always in one place on the disk, so the file handle makes sure you don't have to deal with that.  If you are trying to do something specific with these files, elaborate a little more and there may be some tools out there that will help you do what you'd like without writing any code.