Decrypt WEP wlan profile key using CryptUnprotectData

I am trying to decrypt WEP profile's key using CryptUnprotectData. The way I fetched the profile key is by exporting the profile using netsh.

netsh wlan export profile name="MyWEP" folder="./"

For now, I manually copied the key material from the .xml file generated by the netsh command to my program. And the way, I am decrypting is -

DATA_BLOB DataOut, DataVerify;
DataOut.cbData = encryptData.length();
DataOut.pbData = (BYTE*)("I_Manually_Copy_The_WEP_Key_Here");

if (CryptUnprotectData( &DataOut,
                        NULL,
                        NULL,
                        NULL,
                        NULL,
                        0,
                        &DataVerify))
{
    printf("The decrypted data is: %s\n", DataVerify.pbData);
}
else
{
    printf("Failed. Error Code: %d", GetLastError());
}

But I am getting the error code 13 citing Invalid Data. What am I doing wrong ? On Win 7 and later, I can directly use WlanGetProfile with the parameter WLAN_PROFILE_GET_PLAINTEXT_KEY . But I have NO option on Vista than to use the CryptUnprotectData function. I have seen similar posts here, here but didn't get much useful information. Also, I am using the same system with same user log on credentials. Could any one please suggest me how to proceed ?

PS: I have posted the same question on Windows Desktop SDK forums, but haven't got response yet. Trying my luck on SO.