What is happenning to my computer?

It often auto shut down and when I restart it , windows will say "Windows has just recovered from an unexpected shutdown". This are the details ;- Problem signature: Problem Event Name:BlueScreen OS Version:6.1.7601.2.1.0.768.3 Locale ID:18441 Additional information about the problem: BCCode:3b BCP1:00000000C0000005 BCP2:FFFFF88007C7064F BCP3:FFFFF880096FCA00 BCP4:0000000000000000 OS Version:6_1_7601 Service Pack:1_0 Product:768_1 Files that help describe the problem: C:WindowsMinidump50113-45739-01.dmp C:UsersDominicAppDataLocalTempWER-53633-0.sysdata.xml