What is a TS?
When you boot via PXE, what operating system are you booting?
If it is DOS, then unless you have compatibility mode enabled in the BIOS you are not going to be able to "see" the disk as DOS has no support for SATA.
If it is WinPE, does it have the necessary drivers to support your SATA chipset ? Without those, you will be unable to "see" the disk either. Don't assume the error message is accurate as the disk it may be trying to lock is the virtual one that pxe booted into. Perhaps instead of using /DISK:ALL you should be a bit more specific in order to exclude the disk you have as the boot volume.