Is there any virtual machine which works on a PPC Mac running 10.4?
The primary solution for PowerPC Macs was Microsoft's now-defunct Virtual PC.  It was discontinued several years ago, so you'll really have to do some digging to find a copy.  (Be warned -- it runs slow as molasses.  You'd probably be better off buying a cheap PC.)

There's also Q emulator, which supposedly runs on PowerPC, but I have never tried it.