>I want that my applications should seamlessly encrypt/decrypt all the files (DBFs, CDXs, FPTs. One of the ways i think is to replace the DOS interrupt functions at the start of the application and reinitialise them to the origional state when the application quits.. I will welcome advice if anybody has tried this option. this can cause some problems in a windows environment.. depending on your need - you can either write an encryption routine and pass your sensitve data to that before writing to disk or you can use a 3rd party product lke cryptor who does enryption on the fly there was also apublic domain fll that did encyption , but I don't know the status on that Arnon