All the minidumps crash at SiSGbeXP.sys, which is the driver for your onboard ethernet adapter. See if there's an update on SiS's site.
BugCheck 40000080, {866b56a8, 858aa9b8, 80548d8c, 1} <-- NDIS Driver Bugcheck.
Probably caused by : SiSGbeXP.sys ( SiSGbeXP+4dcd )
f79d3000 f79dac00 SiSGbeXP SiSGbeXP.sys Wed Jun 02 18:13:47 2004 (40BDA85B)