There is lots of help on this topic if you search for "networking" in the archive of helproom.
The best way to network your two PCs (in my opinion) is to link them via a router.
You can get a Linksys router for around £40 from ebuyer.co.uk You will also need network patch cables (RJ45) also from ebuyer.
You may have to drill through a few walls (unless you go for wireless tech - which I don't know about but I believe it is more problematic)
The best thing about linking them via a router is that all PCs on the network enjoy BB without any reduction in speed. Also it means that your main PC does not have to be switched on all of the time for the other PCs to go online.
You do not have to run Win Network wizzard just yet. But once you have established the connection you might want to set up a home network to share files and printers.
However this is very easy if both PCs are using Win XP.
Hope this is enough to get you started.