The versions above were the product of an incremental improvement. I crunched things as far as I could, but sometimes I would start fresh and by taking a different route from the start I managed to shave additional bytes. The latest version is 295 bytes and compatible with XP, Vista, 7 and 8. But the latest version is not ( or at least should not be ) NX bit safe.
Check the first post to grab a copy of the 295 byte version.
In the source code you will find a bitfield that disects tinype at a bit level. It states explicity which bits must be 0, must be 1 or can be toggled freely ( within limits ). This bitfield was built up using a program I wrote that toggled each bit and loaded the resultant image with CreateProcess then tested for errors during CreateProcess or errors in the return value. Then I ran this program on as many PC's as I had access to which included multiple XP systems, one Vista box, multiple Windows 7 systems and just one Windows 8 system.
This bitfield was what I started from when I built the 295 byte version.