Error emcrypting executable files

Hi all,

I´m developing a Filter driver that encrypt files in a directory. It´s ok on
my W2K and WXP machines, but in one machine, running Windows XP, executable
files are not encrypted correctly. I´m disabled Fastio, and all other types
of files (zip files included) are ok.
There is some “protection” about exe files on Windows XP?

Thanks in advance,

Heldai