Network is only working one way

I'm connected to the internet through a cable modem via USB, I'm using a desktop PC with Vista and XP installed(I use vista the most, XP usually just for Games). I decided to share my internet connection with my laptop. So I used a network cable to link my desktop and laptop, when asked by vista I chose a home network, then went to network and sharing center and turned everything off except file sharing and network discovery, I shared some hard disks on the desktop and laptop with privileges to full control. My desktop and laptop's Network cards say 'unidentified network', I don't know why , anyways, then I configured my cable modem to allow other network user's to use the internet connection, so my laptop's NIC now says 'Network' and can connect to the internet, but the desktop's NIC still says 'unidentified Network'... Whys is that?

And Now on to the main topic and the real issue:

After having shared the hard disks of the desktop the same way I shared the hard disks on the laptop, Only the laptop can access files and folders on the desktop PC, but the desktop can't access the laptop's one shared Drive "D:", it denies access to it.

Any help will be greatly appreciated.