Hi subasri,
The way vista handles the Admin/Standard User system, (like the SUDO command in Unix/Linux), is new but the requirement for running programs as a standard user has been in Windows OS from NT so there should be instructions, Somewhere in the VB documentation, to achieve this.
Not being a VB programmer myself, can't help directly on this but you may want to do some research, if you think this is essential in your application. Of course certain operating calls will always need Admin rights to run.