All those accounts and permissions seem to be where most fail here. I won't write at length why you need an account on the machine you are trying to connect to. I also won't write about firewalls.
I have a Laptop with Intel Pro wireless 3945ABG network connection card.
The problem i am facing is that when i am not able to connect to an ad-hoc network. When i create a network people are able to connect to mine but not vice versa.
I use Win Vista Home Premium.