Random computer restart during SP3 install

[TLymphocyte]

this is a fairly old system i built from 2008. i cannot seem to figure out what the problem is, I just bought a new bootdisk today (an ssd)- i figured my old 8-year old HDD had a bunch of bad sectors- and a completely new psu, but whenever i try to install sp3 from an iso (mounted via daemon tools,) after the install extracts all the files and goes into "inspecting your system" or whatever, the computer reboots, every time. this all started to happen when i tried to run shogun 2 total war, computer would reboot right after the first splash screen. creative assembly told me to update my mobo (biostar I945P-A7)driver, which did not fix anything. ever since then, the computer would just restart randomly. i did a clean reformat about a month ago, the restart problem persisted, which means it is no longer a software issue, ran memtest86 via ubuntu cd for 8 hours, no problems there, i have a biostar award phoenix BIOS, which monitors my cpu (pentium D) temperature every time my computer starts, which i've never seen above 20-30C. Another instance where it would restart every time: i do not know if any of you ever play league of legends, but whenever i scroll through the splash arts of champion skins in the store, the system would reboot. I have also tried to clear the CMOS by taking out the battery, did not seem to help.

 

[TLymphocyte]

this is a fairly old system i built from 2008. i cannot seem to figure out what the problem is, I just bought a new bootdisk today (an ssd)- i figured my old 8-year old HDD had a bunch of bad sectors- and a completely new psu, but whenever i try to install sp3 from an iso (mounted via daemon tools,) after the install extracts all the files and goes into "inspecting your system" or whatever, the computer reboots, every time. this all started to happen when i tried to run shogun 2 total war, computer would reboot right after the first splash screen. creative assembly told me to update my mobo (biostar I945P-A7)driver, which did not fix anything. ever since then, the computer would just restart randomly. i did a clean reformat about a month ago, the restart problem persisted, which means it is no longer a software issue, ran memtest86 via ubuntu cd for 8 hours, no problems there, i have a biostar award phoenix BIOS, which monitors my cpu (pentium D) temperature every time my computer starts, which i've never seen above 20-30C. Another instance where it would restart every time: i do not know if any of you ever play league of legends, but whenever i scroll through the splash arts of champion skins in the store, the system would reboot. I have also tried to clear the CMOS by taking out the battery, did not seem to help.

ran some further testing with HWMonitor: i have no idea what any of the temperatures means; THRM: 40C, TMPIN0: 7C, TMPIN1: 86C, TMPIN2: 93C

 

[TLymphocyte]

just cleaned out every particle of dust i can find on the heatsink, reseated the cpu, reapplied the grease, everst still says 93C on the CPU and 86C on the mobo

 

[TLymphocyte]

is there nothing anyone can suggest?

 

[TLymphocyte]

here is another symptom, the computer completely powered off while i was installing microsoft dotnetfix. it was as tho someone just turned off the psu, where the computer completely powered off, then powered back on, then off, then on again.