NTLDR is missing USB boot disk for Windows XP - ntldrismissing.com
Update 2016-01-17: It's possible that "bigger" or "smaller" than 2 gigs makes a difference, if buying a drive, try and buy one bigger than 2 gigs and one smaller than 2 gigs.
http://ntldrismissing.com has boot disks available. Here's the info on how to download the zip file, extract it, format a USB stick, and copy the files needed for fixing the error "ntldr is missing" on Windows XP.
As an alternative, if you can't get it to boot up, try making Hirens Boot USB • Create a Hiren's Boot CD USB Flashdri... their "NTLDR is missing" fix uses my files.
I wish the video wasn't so blurry, and shaky, but I wanted to get this out asap because I keep getting asked for help on this point.
Fat32 has a hard drive limit of 32 gigs; so it's possible you have to use a USB stick smaller than that.