File share/Network set up

Hi, sorry if this has been asked before, but I am having immense problems trying to set up a network using my router to share, transfer & stream files between computers and Android tablets.

Searching the internet has had me going round in circles, with the most common answer being to enable file sharing on the devices & that will magically make everything work. It hasn't!

I'll start with the devices I have already tried, then add the devices I would also like to add:

Thomson 858 router (supplied by ISP)
Desktop PC, Windows Vista Home Premium connected via ethernet
Toshiba Sat Pro Laptop, Windows XP Pro connected via wifi
Samsung Galaxy 2 Tablet, Android, connected via wifi

On each device I have enabled file sharing. Between the Vista & XP machines, I have been able to get the XP to show in Network, but when I click on it I get a "not accesible" error message.

I can't see any sign of the Vista machine on the XP.

When I share files on the Tablet, again it will show in Vista, but when clicked on opens Windows Media Player and only shows what should be on the Vista machine. Again on the Tablet, I can't find the Vista device to share with.

They the devices I have tried. The other devices include:

HP laptop, Windows 7 Home, to connect via wifi
Samsung Netbook, Windows XP Pro, via wifi
2 x Generic Android tablets, via wifi
2 x HTC Andriod phones (not essential but would be nice)

Hoping someone will be able to advise & save my sanity. Thanks for reading & will appreciate any help!