I Need an advise for a lan conexion please

I have a 8 channel switch and 3 computers, in the same room ,other 2 computers are in my sister's house who lives in the house next to mine and we share and paid the bill for more than two years.
the problem is That I need an EXTRA computer that have fully access to the main one wich is the one who has FSX ,in other word like if it were a single one...two computers working like as a single one.
Why:
I need like an assistan computer to see the FSX-SDK (the reading material) the watch direcly the photos of models from airliners.net,while Im working with gmax in the first looking details in the 2nd,and even have Gmax in the second and send the mdls to the FSX run FSX see and correct anomalies of shaping with both Softwares opens or watch tv with a TV lan card while Im in doing other thing in the first one,Like a secondary PC ..
The problem is ,the two
the problem is That I need an EXTRA computer that have fully access to the main one wich is the one who has FSX ,in other word like if it were a single one...two computers working like as a single one.
Why:
I need like an assistan computer to see the FSX-SDK (the reading material) the watch direcly the photos of models from airliners.net,while Im working with gmax in the first looking details in the 2nd,and even have Gmax in the second and send the mdls to the FSX run FSX see and correct anomalies of shaping with both Softwares opens or watch tv with a TV lan card while Im in doing other thing in the first one,Like a secondary PC ..
The problem is ,the two