At my work, we have a few HP dc5850 Athlon X2 desktops that, for some strange reason, have decided to run dog slow over the last week. After testing hardware and swapping units and not finding any resolution, it turns out that a BIOS upgrade solves the problem.
Grab the latest BIOS from support.hp.com. When you run it, it will create a directory in C:\SWSETUP. Use Rufus to turn a USB flash drive into a DOS boot disk (it offers a built in DOS image), and then copy the folder to it. Boot up off of the USB drive, and change to the directory you added, then change to the DosFlash (or "DOSFLA~1") directory. Then run FLASHBIN.
HP really needs to provide a Windows-based BIOS update mechanism.