putenv command on Vista

I am not sure if its vista (you bug me a lot sometimes) or Maya but when I use putenv command to create a custom environment variale it does not save the value. After I set the environment variable and then use "getenv" to read the value it works. But when I restart maya the variable is gone! It's set back to null. This is really annoying.

edit:
It looks like windows does not remember the environment variable itself. So if I use SET command to create a new environment variable then restart command prompt the variable is gone. Does this mean it's limited only for current tsession in vista? I believe when I used this script on XP it did not give me this problem.
I am going to try using Maya.env now.