GVim Portable single instance only

Hi to all

I'm on windows7 pro system.
I use gvim for almost all my editing needs and it works really well.

The strange thing is that only one instance can work at the same time.
For simplicity I will need 2 or 3 instance at the same time and I can't figure how.
At the moment I'm using the portable version and one from the cygwin terminal but's not so easy to handle
^__^

Can someone help me?
Thanks