After installing Windows updates a customer’s HP 6000 Desktop, running Windows 7, would not POST (Power On Self Test). After powering on it would display a HP logo and go no further. I had access to another identical system so I switched the memory, then hard drive and got the same problem both times. I decided to just put the other system in place of that original one. I connected all the cable and got the same problem on the second desktop. At that point I unplugged all but the display and power, since I have seen keyboards cause this type of problem, this time it booted without hanging. I reconnected the mouse and keyboard and it booted fine. I then reconnected the USB printer and it would not POST. I put the original system back in place, without the USB printer connected and it worked fine.
The HP 3005 printer that was connected was bought refurbished and apparently had started affecting the boot process. The decision was made to replace the defective printer so it was retired.