Well, my PC has been rebooting once a day, sometimes (though rarely) twice. Unsure what's going on, I suspect possible driver incompatibility. I have a hijackthis log and 4 most recent (out of 10) minidumps in the attached zip file. Any help will be greatly appreciated.

BugCheck 1000008E, {c000001d, bf805afd, a5632c64, 0}
Probably caused by : win32k.sys ( win32k!RGNMEMOBJ::RGNMEMOBJ+a )

BugCheck 1000000A, {320033, 2, 1, 80513ab2}
Probably caused by : memory_corruption

BugCheck 24, {1902fe, f7a3f9a0, f7a3f69c, 80543e1d}
Probably caused by : Ntfs.sys

BugCheck 100000D1, {1, 9, 8, 1}
Unable to load image AmdK8.sys, Win32 error 0n2
*** WARNING: Unable to verify timestamp for AmdK8.sys
*** ERROR: Module load completed but symbols could not be loaded for AmdK8.sys
Probably caused by : P17.sys (soundblaster live card )

This looks like a memory error within your onboard ram

Please run memtest, by following the following link
http://www.techspot.com/vb/topic62524.html
Report back with findings

Ran through 15 passes and got 5 errors all on test 4. If memtest was supposed to produce a logfile, then it did not for me.

You know I have never run memtest myself (my rams good)
Did it give you a location ie Ram slot 1 or something

But this really means your ram is faulty
You may need to open the case (hardware experience required, also refer to manual for precations, power out)
and reseat your ram (also blow out all dust)

Then you have bad RAM. You'll need to run MemTest on each stick of memory to determine if one or all need to be replaced.