Computer shuts off

[GoldFish_65]

I have an old hp pavilion a847c, running windows xp. The problems started when my son was playing a game online. The game would not load right so he turned off the firewall and virus protection. Later on I started noticing problems with the computer. Outlook express would not display the emails, the bottom section was just gray. The top was normal and I could even change emails but the bottom section would stay gray. The computer also begain to run slow. Webpages would not work, ei: facebooks top bar would not let me click to see messages, comments, etc. So, I went to the virus protection to see. If anything was in quarentened. There was, sorry do not know the name of the trojan and no longer have that info.
So, I did what I normally do, backup all important info and reboot. I do a complete reboot. When the computer was new, I had issues that could not be solved by the backup disks I created, so after talking with HP, they sent me the 8 disk reboot disks. I have done a complete reformat and there is still problems. The first thing I noticed was windows update will not work. I can download the activex file but that is it, I normally manually update, especially after rebooting, but auto updates will not work either. I even rebooted two more times and that did not work. So this last time I decided to download the firewall and virus protection software before I try and get windows update to work. When I when to restart the computer after installing the firewall, the computer keeps running a loop. It starts windows, makes it to the windows welcome screen then restarts.
Any help to narrow what has been damaged by the trojan would be much appreciated!

 

[Chicano]

If you have done a complete reformat and there is still problems, the cause is probably due to hardware issues. If the damage is due to a trojan, it should boot in Safe Mode... so press F8 immediately right after the BIOS posts. Press and hold the F8 key or tap it once a second till the Safe Mode options lists appears on the screen, and select Safe Mode with networking so you can go online to search for solutions and do online virus/malware scans.

If it doesn't boot in Safe Mode the cause may be Hard Drive damage.. the hard drive is what... 8 years old? so that may very well be the problem.. you also need to open the case and check if the processor cooler is running and up to speed, and check for other obvious issues like dirty processor heat sink, lose power or digital connections, if the Power Supply fan is running, if a RAM socket is lose or sockets are dusty, if all capacitors are in good condition... bad caps may be bulged or blown. Also check for BIOS post for possible messages relative to hardware issues. If all checks ok, if you still have the original RAM installed which should be 512MB, see if adding more RAM to at least 1GB (1000MB).. 512MB nowadays is not enough to run a trouble free system. A bad power supply can cause reboots or blue screens and so can an overheating processor so if booting it in Safe Mode doesn't work have the hardware checked and if necessary replaced.

Identifying bad capacitors.
http://www.badcaps.net/pages.php?vid=5