Surface Pro 3 では、Windows インストールを Windows 8.1 では検証されません。

Sysprep was not able to validate your Windows installation. Review the log file at %windir%\system32\Sysprep\panther\setupact.log for details.  After resolving the issue use Sysprep to validate your installation again. 

Reviewing the setupact.log may show the following errors:

2014-11-03 20:57:55, Error                 SYSPRP BitLocker-Sysprep: BitLocker is on for the OS volume. Turn BitLocker off to run Sysprep. (0x80310039)
[gle=0x00000001]
2014-11-03 20:57:55, Error      [0x0f0082] SYSPRP ActionPlatform::LaunchModule: Failure occurred while executing 'ValidateBitLockerState' from C:\Windows\System32\BdeSysprep.dll; dwRet = 0x80310039[gle=0x00000001]
2014-11-03 20:57:55, Error                 SYSPRP SysprepSession::Validate: Error in validating actions from C:\Windows\System32\Sysprep\ActionFiles\Generalize.xml; dwRet = 0x80310039
2014-11-03 20:57:55, Error                 SYSPRP RunPlatformActions:Failed while validating SysprepSession actions; dwRet = 0x80310039
2014-11-03 20:57:55, Error      [0x0f0070] SYSPRP RunExternalDlls:An error occurred while running registry sysprep DLLs, halting sysprep execution. dwRet = 0x80310039
2014-11-03 20:57:55, Error      [0x0f00d8] SYSPRP WinMain:Hit failure while pre-validate sysprep generalize internal providers; hr = 0x80310039

If you run manage-bde -status command it will show the following:

Disk volumes that can be protected with
BitLocker Drive Encryption:
Volume C: [OSDisk]
[OS Volume]

    Size:                 118.34 GB
    BitLocker Version:    2.0
    Conversion Status:    Encryption in Progress
    Percentage Encrypted: 97.8%
    Encryption Method:    AES 128
    Protection Status:    Protection Off
    Lock Status:          Unlocked
    Identification Field: Unknown
    Key Protectors:       None Found