HP Dc7900 Service Reference Guide: HP Compaq dc7900 Business PC - Page 272

Table D-11 Solving Hardware Installation Problems (continued) A new device is not recognized as part of the system. Cause Solution Setup to reconfigure or disable devices to resolve the resource conflict. USB ports on the computer are disabled in Computer Setup. Enter Computer Setup (F10) and enable the USB ports. Computer will not start. Cause Solution Wrong memory modules were used in the upgrade or memory 1. modules were installed in the wrong location. Review the documentation that came with the system to determine if you are using the correct memory modules and to verify the proper installation. NOTE: DIMM 1 must always be installed. 2. Observe the beeps and LED lights on the front of the computer. Beeps and flashing LEDs are codes for specific problems. 3. If you still cannot resolve the issue, contact Customer Support. Power LED flashes Red five times, once every second, followed by a two second pause, and the computer beeps five times. (Beeps stop after fifth iteration but LEDs continue flashing.) Cause Solution Memory is installed incorrectly or is bad. CAUTION: To avoid damage to the DIMMs or the system board, you must unplug the computer power cord before attempting to reseat, install, or remove a DIMM module. 1. Reseat DIMMs. Power on the system. 2. Replace DIMMs one at a time to isolate the faulty module. NOTE: DIMM 1 must always be installed. 3. Replace third-party memory with HP memory. 4. Replace the system board. Power LED flashes Red six times, once every second, followed by a two second pause, and the computer beeps six times. (Beeps stop after fifth iteration but LEDs continue flashing.) Cause Solution Graphics card is not seated properly or is bad, or system board For systems with a graphics card: is bad. 1. Reseat the graphics card. Power on the system. 2. Replace the graphics card. 3. Replace the system board. 260 Appendix D Troubleshooting Without Diagnostics