Answer:How to edit a binary file’s hex value using C#

Position Value
——– ——
0 0x4D
1 0x5A
2 0x90
4 0x03
8 0x04
12 0xFF
13 0xFF
16 0xB8
24 0x40

using (var stream = new FileStream(path, FileMode.Open, FileAccess.ReadWrite)) {
stream.Position = 24;
stream.WriteByte(0x04);
}

ref: http://stackoverflow.com/a/3217953?stw=2