machinetech

I don't know. Could be many reasons. Malware, software bug, registry errors.
I am assuming that your "buisness critical" software is up to date with the latest updates, if your test machines are working fine without the high CPU usage. It could be opening a lot of ports, and keeping them open, even if they are not being used. A large registry with no longer needed entries maybe could cause this, to some degree, with .exe files. Have you tried cleaning and defragging the registry with a good, tried and tested program? Scanned for malware or trojan? I wish I could be more of a help.