Problem to read value of a registry key

I finished the installation of System Center Configuration Manager 2012 here at my company, but I'm having some problems to consolidate the number of installed clients, because I try to delete the customer problem SCCM 2007.

Command I'm using:

$SITECODE=regread("HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\SMS\Mobile Client\","AssignedSiteCode")

I'm sure the key exists (follows a chunk of export record):


Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\SMS\Mobile Client]
"ProductCode"="{D6804B3A-BFEC-4AB4-BFA5-FD9BECC80630}"
"ProductVersion"="5.00.7804.1000"
"PackageCode"="{59A0EA77-D28C-4286-83A6-04BB57B9CDD6}"
"AssignedSiteCode"="001"


Whenever I get a blank value with the command mentioned, I believe that space is the "Mobile Client".

Can someone help me?