The premier archive for "abandonware." While they primarily host ISOs, their forums often have links to pre-installed VHD or QCOW2 images. Archive.org:
qemu-system-i386 -hda windows98.qcow2 -cdrom path/to/windows98.iso -m 256 windows 98 qcow2 full
By default, you're stuck with 16 colors. Projects like SoftGPU provide 32-bit color, high resolutions, and even 3D acceleration for games like Half-Life or Quake . The premier archive for "abandonware