It's in a folder called MultipleMC, in a folder where I put all Minecraft related things, in My Documents.
Anywhere it should be specifically?
No, there are places you shouldn't put it (such as program files and other places that require administrator access), but there isn't a specific place it should be. Make sure it has permissions for the folder, you may even want to try running it as administrator. If you're still having issues after that, message me on IRC.
I'm getting the same error as Steigrudar. My Asus bios Updater starts up when I agree to update. there are no other .exe files in the folders.
Steigrudar, by chance is your motehrboard a Sabertooth x58? if so then our problem may be the software that comes with it indexing the update file. if thats the case forkk13 might just need to gice the exact path of the update prog.
I'll try changing the name of the update file and see if that fixes it.