Linux live not MS Windows if you have a large enough flash drive for a small live for cd distro. It would have to be a "small" distro's iso image. Windows depends on bonding to the systems it's installed onto along with the need for board and other device drivers and drive space available for virtual memory with the creation of a paging file.
Microsoft never came out with a live for cd version of Windows since it has always depended on being installed to a hard drive. Linux on the other is an open source OS with several small as well as larger distros where you might be able to fit one on a larger flash drive and load it by booting from the drive itself.