Hello, as promised I wrote an mbr which performs SHA-1. To squeeze the 
code I had to remove chs and to change the bootdrive installer will have 
to overwrite corresponding instruction. SHA-1 implemented in it is 
little-endian and without padding. Standard version is big-endian and 
with padding. In this case padding is unnecessary since a sector is 
always 512 bytes. Litt-le endian means just that data isn't byte-swapped 
before hashing. And the hash in sector has to be written in little 
endian and the double should be in order
h1,h2,h3,h4,h0
I also implemented the same thing as standalone program
Regards
Vladimir 'phcoder' Serbinenko