Transfer your Windows to virtual
Setup your Windows to accept RDP (Remote Desktop Protocol). Make sure your account permissions allow remote login.
Move your data away from your Windows disk. Save to external disk, cloud, network – what ever you have available.
Resize your C: drive to a maxium size of 127GB. It may be necessary to cleanup your Windows installation by doing a disk clean – remember to include old windows installations which can occupy lots of space.
If you Windows is XP you need a thirdparty tool e.g. http://www.aomeitech.com/download.html
Windows 7, 8.x, 10 use Windows Disk Manager
After resize can consolidate free space using SDelete but it is not a requirement and note if you disk device is SSD – do not use SDelete – it wears the SSD unnecessary.
To convert your installation use Disk2vhd.
The app clones your systems drive C: to the format used by Microsoft HyperV eller VirtualPC.
Remember to set the virtual disk format to the extended format VHDX.
Disk2vhd can save the virtual disk file on the same system but it is better to an external media e.g. removable disk or networkstorage. Ensure enough free space on the destination.