Setting environment variables remotely doesn't work for Windows 7

Question

Hi,
$RemoteMachineList = 'machA', 'machB'
$session = New-PSSession $RemoteMachineList
Invoke-Command -Session $session {[Environment]::SetEnvironmentVariable("Role",0,"Machine")}
The above is the code snippet which I've tried for setting a machine level environment variable. After executing this code in a collection of XP and Windows 7 machines, when I go and check the advanced settings->system environment variables, I can see
the new entry "Role" in all the machines. But unfortunately, this env variables actually gets set only in XP machines(I did a set command from a cmd prompt/or an echo command) whereas in Windows 7 machines, this doesn't exists even though it
shows up in the advanced settings->system environment variables.
Tried in several machines, only Windows XP is yielding the required result.
Please help. 
Thanks in advance ! 
-Aravind

Answer 1

Thanks Chen, but still the same result. 
I'll narrow down the scenario(actually two scenarios) as per the way it's behaving on Windows 7 machines.
Case - 1
1. I do a SetEnvironmentVariable remotely.
2. I go to that remote machine and search in advanced settings -> system env variables window. Dont click on the OK Button.  Close these windows.
Result: Yes it is there as an entry.
3. I open up a command prompt and type 'set'
Result: No it is not set.
4. Again open up advanced settings -> system env variables window. Click on the OK Button.  Close these windows.
5. Now open up a command prompt window and type 'set'
Result: It is set now
Case 2:
1. I do a SetEnvironmentVariable remotely.
2. I go to that remote machine and search in advanced settings -> system env variables window. Dont click on the OK Button.  Close these windows.
Result: Yes it is there as an entry.
3. I open up a command prompt and type 'set'
Result: No it is not set.
4. I do a system restart.
5. Open up a command prompt and type 'set'
Result: It is set now
Any idea why this is behaving like this(more or less like setting a user level env variable), please  ? I've to some way get through this obstacle to advance further. Thanks a lot for the support