This is how MD5 works

This site demonstrate the MD5 algorithm
http://nsfsecurity.pr.erau.edu/crypto/md5.html

other site:
http://en.wikipedia.org/wiki/Md5

Machine ID

Windows Drive serial - API
GetVolumeInformation

For Pentium and above ...
function GetCPUSig : string;
var
TmpPtr : pointer;
begin
Result := StringOfChar(#0, 16);
TmpPtr := @Result[1];
asm
push esi
push ebx
xor eax,eax
mov esi,TmpPtr
cpuid
mov [esi],ebx
mov [esi+4],ecx
mov [esi+8],edx
mov eax,1
cpuid
mov [esi+12],eax
pop ebx
pop esi
end;
end;

Motherboard and Bios Info (serial and date)

HKEY_LOCAL_MACHINE\HARDWARE\DESCRIPTION\System\SystemBiosVersion
HKEY_LOCAL_MACHINE\HARDWARE\DESCRIPTION\System\SystemBiosDate

HDD manufacturer 's serial

http://www.winsim.com/diskid32/diskid32.html