If you also continue reading my post where i asked why you cannot use a router, i did also mention some info about how it can be done. I cannot give you specific links or info (as i don't actually know myself) but if you do some Googling for Soft AP's you will find the answers.
"Base Stations" as Apple call them are known as "Wireless Access Points" in the PC world, what you're after is a Software Access point. Much like a software firewall.
As nobody else is jumping in with "The Answer" i can only suggest you do some research yourself using the little bit of info i have given, sorry but that's all the help i can give.
EDIT:
In the WiFi cards properties there will be a "Mode" selection somewhere with options like
Infrastructure and
Ad-Hoc, if you're lucky it will have an
Access Point mode to do what you need.
Either way I suppose asking in the Mac forum was a bad idea to begin with.
I am a Mac noob myself, been using Windows all my life.
But after explaining what I was trying to do the second time I figured it was clear that I did not want to use a router.
Well the way you worded your post made it sound like there was some ungodly reason for you not being able to use a router, i merely asked why to see if the reason you absolutely couldn't use one was based on a misconception that could be fixed.
I'm really not trying to argue and just want to help, sorry if i worded it all wrong. It's late (like 4am late) and i'm suffering sleep deprivation