C# Definition:

[Flags]
enum ShutdownReason
{
    MajorApplication = 0x00040000,
    MajorHardware = 0x00010000,
    MajorLegacyApi = 0x00070000,
    MajorOperatingSystem = 0x00020000,
    MajorOther = 0x00000000,
    MajorPower = 0x00060000,
    MajorSoftware = 0x00030000,
    MajorSystem = 0x00050000,

    MinorBlueScreen = 0x0000000F,
    MinorCordUnplugged = 0x0000000b,
    MinorDisk = 0x00000007,
    MinorEnvironment = 0x0000000c,
    MinorHardwareDriver = 0x0000000d,
    MinorHotfix = 0x00000011,
    MinorHung = 0x00000005,
    MinorInstallation = 0x00000002,
    MinorMaintenance = 0x00000001,
    MinorMMC = 0x00000019,
    MinorNetworkConnectivity = 0x00000014,
    MinorNetworkCard = 0x00000009,
    MinorOther = 0x00000000,
    MinorOtherDriver = 0x0000000e,
    MinorPowerSupply = 0x0000000a,
    MinorProcessor = 0x00000008,
    MinorReconfig = 0x00000004,
    MinorSecurity = 0x00000013,
    MinorSecurityFix = 0x00000012,
    MinorSecurityFixUninstall = 0x00000018,
    MinorServicePack = 0x00000010,
    MinorServicePackUninstall = 0x00000016,
    MinorTermSrv = 0x00000020,
    MinorUnstable = 0x00000006,
    MinorUpgrade = 0x00000003,
    MinorWMI = 0x00000015,

    FlagUserDefined = 0x40000000,
    FlagPlanned = 0x80000000
}

VB Definition:

Enum ShutdownReason
    MajorApplication = 0x00040000
    MajorHardware = 0x00010000
    MajorLegacyApi = 0x00070000
    MajorOperatingSystem = 0x00020000
    MajorOther = 0x00000000
    MajorPower = 0x00060000
    MajorSoftware = 0x00030000
    MajorSystem = 0x00050000

    MinorBlueScreen = 0x0000000F
    MinorCordUnplugged = 0x0000000b
    MinorDisk = 0x00000007
    MinorEnvironment = 0x0000000c
    MinorHardwareDriver = 0x0000000d
    MinorHotfix = 0x00000011
    MinorHung = 0x00000005
    MinorInstallation = 0x00000002
    MinorMaintenance = 0x00000001
    MinorMMC = 0x00000019
    MinorNetworkConnectivity = 0x00000014
    MinorNetworkCard = 0x00000009
    MinorOther = 0x00000000
    MinorOtherDriver = 0x0000000e
    MinorPowerSupply = 0x0000000a
    MinorProcessor = 0x00000008
    MinorReconfig = 0x00000004
    MinorSecurity = 0x00000013
    MinorSecurityFix = 0x00000012
    MinorSecurityFixUninstall = 0x00000018
    MinorServicePack = 0x00000010
    MinorServicePackUninstall = 0x00000016
    MinorTermSrv = 0x00000020
    MinorUnstable = 0x00000006
    MinorUpgrade = 0x00000003
    MinorWMI = 0x00000015

    FlagUserDefined = 0x40000000
    FlagPlanned = 0x80000000
End Enum

Notes:

Major flags should be combined with minor flags. For more info on these combinations see:

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/sysinfo/base/system_shutdown_reason_codes.asp