This issue occurs when the Helper Virtual Machine deployed by vCenter Converter Standalone runs out of system memory before completing the conversion process.
Resolution
To resolve this issue, increase the memory of the Helper Virtual Machine.
To increase the memory on the Helper Virtual Machine:
Initiate the conversion process.
After creating the Helper Virtual Machine within vCenter Server, power off the Helper Virtual Machine.
Edit the virtual machine settings to increase the amount of memory.
Power on the Helper Virtual Machine.
Remount the Helper ISO image (converter-helper-vm.iso or converter-helper-vm-x64.iso) to the virtual machine.
Note: This image is located at C:\Program Files (x86)\VMware\VMware vCenter Converter Standalone on the machine in which vCenter Converter Standalone is installed. During the conversion process, the image is mounted. However, by interrupting this process when modifying the memory on the Helper Virtual Machine, you must remount the image.
Press CTRL-ALT-DEL on the virtual machine to start from the ISO image.