This script from XDA can be used to extract the key, just save it as .bat and run it.
::' Windows RT 8.0 Product Key Dumper by Myria of xda-developers.com ::' Original Windows 8.0 VBScript by janek2012 of mydigitallife.info ::' Batch+VBScript hybrid trick by dbenham of stackoverflow.com ::' Fix for keys starting with N by Osprey00 of xda-developers.com ::' ::' Windows RT doesn't let unsigned VBScript use WScript.Shell, which is ::' required in order to read the registry in VBScript. So instead, we ::' have a batch file call reg.exe to do the registry lookup for us, then ::' execute the VBScript code. Might as well do things this way, since ::' it would really suck to write this math in batch... ::' --- Batch portion --------- rem^ &@echo off rem^ &call :'sub ::' If we were run from double-clicking in Explorer, pause. rem^ &if %0 == "%~0" pause rem^ &exit /b 0 :'sub ::' Read the registry key into VBScript's stdin. rem^ &("%SystemRoot%\System32\reg.exe" query "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion" /v DigitalProductId | cscript //nologo //e:vbscript "%~f0") ::'rem^ &echo end batch rem^ &exit /b 0 '----- VBS portion ------------ 'WScript.Echo "begin VBS" ' Get registry data that was piped in RegData = "" Do While Not WScript.StdIn.AtEndOfStream RegData = RegData & WScript.StdIn.ReadAll Loop ' Remove any carriage returns RegData = Replace(RegData, ChrW(13), "") ' Split into lines RegLines = Split(RegData, ChrW(10)) ' Sanity checking on data If (RegLines(0) <> "") Or (RegLines(1) <> "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion") Then WScript.Echo "Got invalid header trying to run reg.exe" WScript.Quit(1) End If If Left(RegLines(2), 38) <> " DigitalProductId REG_BINARY " Then WScript.Echo "Got invalid value list trying to run reg.exe" WScript.Quit(1) End If ' Get hex string HexString = Mid(RegLines(2), 39) If (Len(HexString) Mod 2) <> 0 Then WScript.Echo "Got an odd number of hex digits in REG_BINARY data" WScript.Quit(1) End If ' Convert to byte array Dim ByteArray() ReDim ByteArray((Len(HexString) / 2) - 1) ' VBScript is just weird with array dimensions >.< For i = 0 To (Len(HexString) - 2) Step 2 ByteArray(i / 2) = CInt("&H" + Mid(HexString, i + 1, 2)) Next Key = ConvertToKey(ByteArray) WScript.Echo Key ' janek2012's magic decoding function Function ConvertToKey(Key) Const KeyOffset = 52 ' Offset of the first byte of key in DigitalProductId - helps in loops isWin8 = (Key(66) \ 8) And 1 ' Check if it's Windows 8 here... Key(66) = (Key(66) And &HF7) Or ((isWin8 And 2) * 4) ' Replace 66 byte with logical result Chars = "BCDFGHJKMPQRTVWXY2346789" ' Characters used in Windows key ' Standard Base24 decoding... For i = 24 To 0 Step -1 Cur = 0 For X = 14 To 0 Step -1 Cur = Cur * 256 Cur = Key(X + KeyOffset) + Cur Key(X + KeyOffset) = (Cur \ 24) Cur = Cur Mod 24 Next KeyOutput = Mid(Chars, Cur + 1, 1) & KeyOutput Last = Cur Next ' If it's Windows 8, put "N" in the right place If (isWin8 = 1) Then keypart1 = Mid(KeyOutput, 2, Cur) insert = "N" KeyOutput = keypart1 & insert & Mid(KeyOutput, Cur + 2) End If ' Divide keys to 5-character parts a = Mid(KeyOutput, 1, 5) b = Mid(KeyOutput, 6, 5) c = Mid(KeyOutput, 11, 5) d = Mid(KeyOutput, 16, 5) e = Mid(KeyOutput, 21, 5) ' And join them again adding dashes ConvertToKey = a & "-" & b & "-" & c & "-" & d & "-" & e ' The result of this function is now the actual product key End Function