How can I run Windows Software .exe on a PowerBook G4?
VirtualPC is the most stable option, but x86 -> PowerPC instruction emulation is slow and cannot be used to play games at all, unless it's legendary Solitaire.

Mac OS X 10.4 is the fastest OS X system you can find for PowerPC Mac, but the system itself will eat 512 MB from available RAM for adequate speed and that leaves you with 256 MB for Windows, not enough to run Windows XP, maybe Windows 95?