MobaLiveCD is a QEMU (a generic open source emulator and virtualizer) based stand-alone emulator, that lets you run Linux Live CDs on Windows without the need of any Windows configuration or extra hardware.
Its portability — it takes just about 1.6MB of your hard/flash drive, together with its intuitive interface makes it rather easy-to-use. With the emulator running all you have to do is point it to your downloaded ISO image to get the Linux OS on Windows. MobaLiveCD also has a right-click function, installed, it lets you launch ISO images with the right-click menu.
Authors Note: I tested MobaLiveCD on Windows XP sp2, with Puppy Linux; Xvesa, using a non-admin account, it loaded this small Linux OS in no time without any issues, but browsing was rather too slow, or almost impossible.