This is my first post, I hope I'm in the right spot. Here is my deal:
1.- Got a hold of an HP Pavilion a642n which was already abandoned by the owner as unfixable and replaced by a new DELL.
2.- Plugged it on and it purred on past the Windows XP HOME EDITION banner, went into Checkdisk and proceeded to record numerous bad allocations, fast job and just as fast it quit! Just went black until I turned off.
3.-Like a nut, eager to put apart my new toy, I didn't hesitate, I tored into that case, disassemble the HDD and plugged it into my VISTA Comp. Surprise! It did the same thing, it went into Checkdisk only this time Checkdisk fixed all problems and it booted! HalleluYah!
4.- Perhaps I sang victory too soon for when I plugged the drive back into the HP computer it no longer booted, but, then I realized that I had the option to press F10 and let HP take care of restoring the original config and finally it booted perfectly.
5.-When it started the recovered XP HOME EDITION I began to clean up everything including the registry. I wanted to install the free AVG 8 ANTIVIRUS and it required the service pack 2. I installed the pack but I didn't installed any other updates prior to it. After Service Pack 2 installation it attempted to restar Windows. This was the first restar since the recovery.
6.- As it was supposed to restar it only shut Windows, flashed a "NO SIGNAL" error and went into a black screen but it didn't restar.
7.- Turned off comp. after a while and then on. It began reboot process flashed HP banner then a black screen then a line with a series of vertical lines, it took a while but eventually it went through the whole line of vertical lines, flashed the Windows XP logo and finally got to the Welcome and desktop.
8.-Tried to restar again. Same No Signal error. Turned Off and On and this time I pressed F10 again and recover the system a second time.
9.- This time when it finally opened Windows I just clicked to install updates. It installed 61 updates and required restar. Same situation with the NO SIGNAL error.
10,- Turned off and on and when it eventually loaded Windows after the line of vertical lines and all flashes of Windows banners and Welcome screen.
11.- This time it wanted to install updates again. I clicked to install updates. It installed 1 update: Windows Service Pack 2 and went into restar and No Signal error again.
12.-This time when it went into desktop it flashed, "your computer might be at risk, no Antivirus." I proceeded to install the Free Avg 8 and googled the 'NO SIGNAL ERROR" clicked the first link and got to your site.
13.- I connected my USB printer and printed the posts about the NO SIGNAL error. I followed all instructions to a point for the Video card is stuck and I can't get it off the PCI slot. I did pressed and made sure that the card was properly seated and checked the cable. The cable connector is missing one little prong so I plugged the comp. to a brand new monitor with the same results, so it's not the monitor's fault.
14.- So, I registered and now I'm posting this in hopes that somebody can figure out what should I do next to get the computer to restar on its own.
15.- I would like to check the MB but I don't know how. I'm taking an A+ CERTIFICATION course on line and I'm learning the way but I got a long ways to go. This situation with the HP computer is one of the issues I'm dealing with. I am 69 years old, a writer and believer of the WAY of Yahushua, our Savior. I'm not into religion just living this blessed life style which includes the computer world. I've been dealing with these machines since 1985 on my own and this is kind of the first time that I am seeking professional help and, blessed I am to have found your site. I want to learn the technical in and outs of the computer world in order to help out all my pauper friends who had no money or time to fix their mess up computers. It's sort like a ministry and a well needed service in my midst. Pray that you all brilliant gurus take pity on me and help me out in this endeavor.

Check disk. Is that a method of reformatting?

I mean, if the person who dumped it said it was beyond repairable, you have to start everything from scratch. Video card, memory, everything.