Ebuyer 4 Port Cable/DSL Broadband Router with Print server £15.27 click here
connect your modem with this router's uplink (via ethernet cable) and both PC connect to this router's downlins via Ethernet.
If your PCs have not got any Ethernet (Lan) connection port, you need to fit a PCI network adaptor: Ebuyer 10/100 Network Card with wake on Lan - Retail Box £2.50 click here.
If you do not want to open up PC to fit network adaptor, you can get a USB version: Dynamode USB 10/100 Rj45 Adapter £6.96 click here.
The ethernet cable is called "Cat5e" cable, you can get from ebuyer as well, very cheap.
Since two PC access net independently, the virus/spyware defence should be installed on both PC.