If you do have another drive that can boot Windows 7, you can use the Disk Management tool to build a new system partition on your existing SATA drive. You have to shrink the existing partition, and create a new partition. Then you can copy the boot files to the new partition using bcdboot.
An APU is an auxiliary power unit. On-board APUs are small jet turboshaft engines that are started to provide electrical and hydraulic power to the aircraft when needed during periods when the engines aren't running. Some aircraft are designed...
A GPU is a type of APU for graphics. A PPU is a type of APU for physics. A GPU might even one day become another APU just for the GPU, specialized for realtime raytracing or Sparse_voxel_octrees. There are manufacturers that will produce a customized APU optimized for what you want it to do.