1. buy or make crossoever cable,
2. make sure each computer has ethernet card installed, driver loaded, and configured.
3. connect both using crossover cable
4. ping one from another pc to see if hardware connection is ok
5. make sure file sharing is loaded
6. share one folder or whole harddrive on one pc, then map it as a drive on another.
hints:
2. configuration can look like
PC1 IP 192.168.0.1
PC2 IP 192.168.0.2
and both will have subnet mask 255.255.255.0
4.
open dos box and type
ping 192.168.0.1
6.
if both PCs are part of same workgroup or domain you can browse networking and find the shared folders, printers etc.
you can also map it directly:
for example on PC1 you rightclick on folder C:\shared and under sharing select it is shared and choose if others will have
only read or both read and write access. choose name to share it, something like "pc1_shared" (without quotes)
go to other pc, open windows expolorer, from tools menu select map network drive, pick new drive letter (W: or something)
and as path type "\\192.168.0.1\pc1_shared" (without quotes).
If you plan on adding more computers, don't bother with crossover, get a hub or switch or router and couple of straight cables.
note that many new ethernet devices (switches, network cards etc.) don't care if you have straight or crossover.
they detect and automatically select proper connection.
if you have one of PCs on a internet, it would be good idea to allow internet access for the other PC as well.
newer windows versions have internet sharing but there are free proxy servers like AnalogX that work nice too.