I have been having this problem too of Skyrim causing my computer to crash and reboot with a hypertransport sync flood error on last boot.
Windows Vista Premium Edition 64 bit Service Pack 2
ATI Radeon HD 5700 Series
AMD Phenom 8250e Tri-Core processor rated at 1.9ghz (minimum says 2.0ghz dual core run other dual core 2.0 speed games just fine)
4 gigs of ram (I forget who the manufacturer is for my ram)
It's not a heat issue because the processor never went over the same heat as the OPs.
Attempted fixes: BIOS flash, HT speed reduction from default 1800 to 16000 then to 14000 (I can't adjust the Northbridge speed), updated graphic drivers, changed from the first time set-up auto detect settings to low (believe settings were set to medium on the auto-detect) and the sound fix on forums of turning down the sound quality to that of cd quality on Vista.
Other games tested to see if other games could cause crash: World of Warcraft, Dragon Age 2, Witcher 2, Deus Ex Human Revolution, Team Fortress 2 and League of Legends.
Only level 8 and has been happening since I was going to Whiterun for the first time. Doesn't happen while in dungeons/caves or in Whiterun itself only on world map. This has also only happened with Skyrim. I'm thinking it's Skyrim or my processor, while passing on the Can you run it site (I check there before buying PC games), isn't good enough to run Skyrim because of it's speed.