Hi,
After reading your minidumps, I find out two culprits. The first culprit is faulty mother board and the second culprit is Norton AV.
Sugestion
1. Replace the motherboard.
2. Your version of Norton AV has known bug. De-install or upgrade Norton AV.
Debug Report
Mini020206-01.dmp BugCheck 100000D1, {868914e8, a, 0, f6553950}
Probably caused by : ALCXWDM.SYS ( ALCXWDM+34950 )
Mini021706-01.dmp BugCheck 1000008E, {c0000005, 80571eae, b9fe1b5c, 0}
Probably caused by : SYMEVENT.SYS ( SYMEVENT+11bf9 ) <-- Norton AV
Mini032506-01.dmp BugCheck 10000050, {bbe583ff, 1, bf80f24d, 2}
Probably caused by : hardware ( win32k!NtUserGetMessage+26 )
Mini040106-01.dmp BugCheck 1000008E, {c0000005, 4983f4c2, b5c4db08, 0}
Probably caused by : hardware <-- Faulty Motherboard
Mini040106-02.dmp BugCheck 100000D1, {3e, a, 0, f63e4956}
Probably caused by : ALCXWDM.SYS ( ALCXWDM+34956 )