right, you need to set up on the main pc to share a connection, the tesco one..
duplicate the tesco connection and call one of them "shared tesco" (so that you use the other if you only want to use it on one pc)
in the waizard for setting up a network (accessed on left hand side) you select that THIS computer has the connection, and choose a network name you can rememberr eg. HOME
on the other set it up the other way round, the other pc ahs the connection. Now use the same network name, but a different computer name
now dinnect the internet thru pc 1 and plug in the second pc
should have access. if you want to transfer files, go to start menu - run and type in \\computername
computername is the name of the other pc...
then the files you have opted to share on the other pc will come up..
to share more files, right click, properties, sharing, share as...