Megasquirt and 64bit OS.
 

I know MS-I is older and and you can get ms 2 and ms 3 kits now but if you do have or get ms1 then give this a read.

So if you decide to do MS-I on your vehicle, and if you have to load firmware to your board using windows but 64 bit version you will find that the regular download-firmware.bat that you need to open from your code files will not work as its not compatible with 64bit OS. Instead you have to go to http://www.megamanual.com/ms2/code.htm and download the MS II down-loader and use this to burn your firmware but you have to set the com speed to 9600.

Edit: Give this a try, I am not home yet so I cant confirm this yet but as soon as I try it out I will update on how to do it if anything special is required.

UPDATE:

I just tried this for last few days and I could not get it to work at all..

What I did was:

Found an old xp 32bit install disc, made a new partition of 10 Gigs on my hard drive (can be less), installed XP onto it with Tunerstudio on it and now I dual boot into XP for MS. It worked this way.