I have a hp7850 pavilion which sat on the floor for a year or two. I was going to give it to a SCHOOL but after plugging it in it just turns on and nothing else. The light comes on that its on but nothing else happens. I can't turn it on or off with the start button, also there is a cd-rom light on but that will not open or close or do anything either. The only way to turn this on or off is to pull the plug or plug it in to get a light. Please help
JoeCheck all connections, if ok then i would first point the problem as the POWER supplylostmymsdos, Are you holding in the "off" button long enough when you are attempting the SHUT down--sometimes it can take about 10-20 seconds ? Also you should check that all internal components are securely connected--particularly the HHD and RAM connections. While you have the case open clean it out if it looks dusty. Also at that time ensure that the fans are running --the CPU fan and the PSU fan. Don't open the PSU cage. Why has it been "sitting" around that long? Did you stop using it because it wasn't working properly? truenorthThanks for the replies --I set the computer aside because I upgraded to a newer computer---I am holding the startshutoff button in for 20 sec's plus--I removed the cover and its very clean inside---The fans are working--I'm wondering if the harddrive is frozen---This was a computer that was on a lot--Any more ideas out there---One more thing---When I plug in the computer it is on automatically--That in itself is strange--Thanks again Joe I would start from scratch in oder to illiminate possible hardware failures.
Is it a PSU problem, RAM, CPU or Motherboard? Check these first. How?

Disconnect A/C power from systems unit. Disconnect your HD and optical drives and FDD, card readers, mouse, keyboard . Reconnect the power supply and observe immediately that the CPU fan is operating, the case fan is turning as well as the PSU cooling fan. If any of these are not working then switch off immediately and check connections. Is there a single "beep" from the internal speaker." Is there multiple "beeps" from the speaker? If so check the beep codes to see what they relate to. Are there any messages on the monitor. If there is nothing at all, is the monitor receiving a signal from the system, some will have a orange light for power on and this will change to green when a signal from the system is received. Have you checked the CMOS battery? (3v) If you are handy with a volt meter, check the voltages of your PSU especially the 20-24 pin ATX power connector. Is the power switch on the FRONT of the case U/S? Check by disconnecting it from the motherboard. Use a screw driver to short across the PWR switch pins to fire up the system. Also check to see if you have anything in the DVD drive which might be preventing the system powering up. Look at the front of the drive for a small pin hole and if there is one, use a PAPER clip to release the mechanism. If you have a spare stick of RAM, replace it with the one fitted and try again. If the Power supply is defective you will have to replace it. CPU might be the next suspect and finally the mother board. If the system shows signs of life in these basic checks, reconnect each of the drives one by one and try each one at a time. If you have another system in use you can always check a suspect hard drive in that system. These are just a few thoughts which might help. Above all check and recheck your connection and the seating of power cables, Ram and CPU. Even if the problem is not solve you can illiminate many of the usual suspects. Remember to protect against ESD when handling sensitive components. Good Luck.