iBooks are PowerPC-based Mac notebooks.
You can't run Intel versions of Windows on the "bare metal" of machines with different machine code architectures (e.g., 68K, PowerPC, ARM / Apple Silicon). So something like SoftWindows or Virtual PC would have been the only way to run Windows on an iBook.
Footnote:
There was a version of Windows NT that ran on IBM workstations with Power-architecture CPUs, but I don't believe that it was ever released for PowerPC-based Macs. Applications had to be built for it - it had no Intel emulation, or Rosetta-style translation, to allow it to run off-the-shelf Windows/Intel applications.