CPU overheatsToshiba Satellite A105-S4134 need to replace system board and cpu

Apparently so. Here you go:
http://forums.toshiba.com/t5/Satellite-Laptops-A-Series/cpu-upgrade/td-p/253167

If your laptop appears to boot up and the hard disk LED flashes, then the problem is probably a back light fault. This can be a faulty inverter or a faulty CCFL lamp. Please click on this link and follow my instructions to identify the fault and possible fix :- http://www.fixya.com/support/r3598095-faulty_laptop_lcd_screen

Greetings,

Download the user guide at the following Toshiba website.

http://www.csd.toshiba.com/cgi-bin/tais/support/jsp/modelContent.jsp?ct=DL&os=&category=&moid=1364545&rpn=PSAA8U&modelFilter=A105-S4134&selCategory=2756709&selFamily=1073768663

ALSO, very important there is a BIOS update that is critical for that laptop you should follow the instructions on the Support News tab.

check whether your electrical socket where u pluf the charger is earthed or grounded .If its not grounded it will burn your charger

I hope this will help you
good luck

OK, I would restore or recover the computer to manufacturer's original specifications and automatic update to the latest sp3.

Then, I would reinstall your virus protection and see if it's better.

Go yo this link below, this will show toy step by step... http://windows.microsoft.com/en-US/windows-vista/Burn-a-CD-or-DVD

Honestly, it is normally not worth it to upgrade the cpu on a laptop. Laptops are build to deal with a certain amount of heat and adding a faster cpu can cause the current cpu cooling fans to not get the job done anymore. You will seem instability in your system and could possibly damage it due to over heating.

With that said you would only be able to upgrade to a very slightly higher speed cpu and your money would be better spent else where. Some good ways to speed up a laptop are max out your memory or install a faster hard drive. For example if your current drive is a stock 5400rpm unit a 7200rpm drive would give you a nice boost. You could also look into a solid state option.

Both these upgrades will give your laptop a better boost without the hassle and risk of a cpu upgrade.

here is your driver:
http://www.csd.toshiba.com/cgi-bin/tais/support/jsp/modelContent.jsp?ct=DL&os=&category=&moid=1364545&rpn=PSAA8U&modelFilter=A105-S4134&selCategory=3&selFamily=1073768663

To upgrade the cpu, you will still need to use the same type of cpu. A socket 478 motherboard will not work with a socket 775 processor. The pin configuration is different.

Have you checked the heat of CPU? It might be cause of CPU overheating.