i Have once computer with windows 7 in a room and another with windows xp in the other. I also have an hp printer and a wireless router and the lan cables and everything. How can i send files between the two computers and send files from a computer to the printer to be printed ?
File swapping -- you need to start the Networking Wizard and follow that. But make sure to turn off Windows or other firewalls on the machines while setting up. Make a note of the computers' names (Control Panel, System).
Enable file sharing in the relevant folders on both machines. Go to My Network Places, Add a Network Place (and go and make a nice cup of tea to calm you during that process as it's sometimes quite pedantic and slow, thanks Microsoft).
I would also advise doing this initially with the computers linked by ethernet not wireless (either a crossover cable between the computers or straight-thru cables via the router)
Printers ? -- figure those out later once you've passed your baptism into networking.