I have an HP Pavilion 310n which I purchased brand new in 2002. A while ago, it began to cease normal function. It would boot up all the way until the black screen with the windows logo and the loading meter, and then the computer would suddenly turn off, and then turn back on all by itself and repeat this never ending process. At first, I thought it could be the power control unit because the fan was not functioning normally. It would go slow and sometimes hardly at all. I replaced the pcu and still no luck—same never ending occurrence, so I sent the new pcu back and put the old one in after I cleaned it and the computer from all dust that could potentially inhibit it from normal function. The fan was working better on boot but still the computer would perform the never ending sequence. It was time to upgrade anyway so I bought a new computer and let it collect dust, but now I’ve taken it out again to try to fix. I recently left it with a computer specialist and he told me that it needed and new hard drive because the computer was not recognizing the drive. I didn’t want to pay for him to fix it so I brought it home an ran some tests myself. Upon boot, the computer went to a black screen and read “operating system not found.” I took the hard drive out and set it as a secondary drive in my new computer. I reformatted it successfully and it worked as a storage drive. I then installed windows XP on the drive and that was also successful. I then took the drive and put it back in the old computer and it still would not recognize the drive. I checked the bios and the boot sequence was set to CD-ROM then Hard Drive. I used the windows XP installation disk to run the recovery console. I rewrote the Master Boot Record using the “fixmbr \Device\Harddisk0\Partition1” command which was given from the “map” command. That did not work so I then entered the recovery console again and entered the command “fixboot” to rewrite partition boot record. If someone could help me diagnose this issue, I would greatly appreciate it.