the computer has rebooted from a bugcheck

Hi all

in the past 2 days my computer has been rebooting itself
as you can see in the following event :

the computer has rebooted from a bugcheck
The bugcheck was: 0x100000d1 (0x0000008b, 0x00000002, 0x00000001, 0xb30bea08). A dump was saved in: C:\WINDOWS\Minidump\Mini021407-01.dmp.

can someone please tell me why is it happening?

minidumps are attached...

Your windows is crashed without pattern and this is the symptom of faulty ram. Run memtest to stress test the ram.

Mini010807-01.dmp BugCheck 100000D1, {14, 2, 0, f87179c6}
Probably caused by : Cdfs.SYS ( Cdfs!CdCheckForDismount+82 )

Mini010907-01.dmp BugCheck 100000D1, {14, 2, 0, f87179c6}
Probably caused by : Cdfs.SYS ( Cdfs!CdCheckForDismount+82 )

Mini020307-01.dmp BugCheck 100000D1, {1014, 2, 0, f7eb5f82}
Probably caused by : ALCXSENS.SYS ( ALCXSENS+57f82 )

Mini021307-01.dmp BugCheck 1000008E, {c0000005, bf8022c1, b10c6c74, 0}
Probably caused by : win32k.sys ( win32k!xxxInternalGetMessage+d )

Mini021407-01.dmp BugCheck 100000D1, {8b, 2, 1, b30bea08}
Probably caused by : symidsco.sys ( symidsco+23bfc )