1. actually it would be sufficient for now to handle local files and those one local network; 2. once again: the files would be readed sequentially, so I think that a 30MB cache per file is quite enough; on exceptions (random reads) doesn't maters the caching performance 3. if you have some time, PLEASE send me an example of how could I do a file caching for an intercepted handle; (this example would be really valuable, as I have no deep knowledge about NT api / Visual C++; I'm actually a Delphi / Database / Assembly programmer; ... and I'm only 19 years old :)) 4. where can I find some links to that Microsoft "file system filter driver DDK"? thanks, Sandor