To get fast VMs, you need the guest OS (in this case, Windows) to be built for the same CPU architecture, and preferably to have virtualization features on the CPU. Since you're not likely to get either, you'd have to emulate the CPU. QEMU can do it, but it'll be slow.
On the other hand, if Windows 98 is enough for you, you can run it on your phone right now: http://copy.sh/v86/?profile=windows98
That site is doing the CPU emulation in JavaScript(!). It's fast enough because, well, it's Windows 98.