You could attempt to move to a VM, this'll likely fail. I know a KVM environment should work theoretically but it may not. If that fails you'll likely need to

You could attempt to move to a VM, this'll likely fail. I know a KVM environment should work theoretically but it may not. If that fails you'll likely need to go with an air gap. Transfer all data in and out via flash drive and run nightly virus scans on host computer and the XP one. If you can't air gap the XP computer. Nightly virus/mal scans, allocate more time for IT preemptively, and maybe prayer? Weekly/Monthly hard drive images are likely a good idea also. :.:.: Also stock pile old hardware for it. Trying keeping a few functional ATA hard drives on hand, spare PCI cards if you need them. In all honesty have 1 or 2 computers that can serve as drop in replacements on failure is likely a good idea.