For the sake of the OP's original question: moving to qemu is possible. It all depends on the setup within the
7.4 system. But generally it's easier to first install FreeBSD and then move the application to it. My assumpiton: qemu host has graphics output. If not, you can play with the
-console,
-vnc and alike options to get the job done.
On a qemu host you could do the following:
Download the old FreeBSD from the archive
here.
Prepare the virtual disk:
qemu-img create -f qcow2 qbsd7.qcow2 10g
Launch the FreeBSD installer:
qemu-system-x86_64 -hda qbsd7.qcow2 -cdrom FreeBSD-7.4-RELEASE-amd64-disc1.iso
Follow through the installation process and boot to the newly installed system. Then you can start migrating the application from old physical system to new virtual.
There's also an option to play with the virtio drivers to get the better performance out of it (I don't know if virtio drivers are supported on
7.4)
Again, there are more ways to skin a cat, this is one of them.