NTLite cannot capture a live system image, but it can be done by DISM. For best results, you first boot into WinPE (with no unattended file) or Windows Recovery, so your live Windows isn't running (quiet).
1. Open a CMD window from WinPE, with
Shift-F10. Run DISM to capture the mounted C: volume.
Code:
DISM /Capture-Image /ImageFile:"C:\path\to\install.wim" /CaptureDir:C:\ /Name:"My Windows"
2. Restart normal Windows. Move your captured install.wim to your ISO folder's \sources folder, and overwrite the existing file.