When trying to link and share files between two PC using Microsoft Networking, I found the following points should be noted:

• The UTP cable should be crossed.
• TCP/IP and NetBEUI protocols should be set in the Control Panel networking dialog box.
• Don't forget to enable file sharing in the same dialog box.
• You have to login in Microsoft Networking, just pressing Escape or Cancel at the login / password prompt will give you "not able to browse network" error. Use the Start > Logoff menu command to re login correctly.
• I used to think that you must be in the same workgroup to share, but I've confirmed that is not the case.
• You don't have to reboot, after connecting the UTP cable, just re login is good enough.
• If there are lights on the NIC, then you have physical layer connection okay. Normally green light shows network activity by blinking, and yellow light shows 100 Mbps connection, and 10 Mbps if no yellow light.
• CIFS: Common Insecurities Fail Scrutiny is required reading, for further insights.

Actually, netBEUI doesn't need to be installed at all. The items you need (under w9x) are

Client for microsoft networks
TCP/IP
Network Adaptor
File and print sharing for microsoft networks (on at least one of them).

If you have a dial-up adaptor, make sure File and print sharing for microsoft networks is not bound to it.
If your machines are in different workgroups, you can still share files, but you need to go through either entire network, or find computer to see each other.
If you're using 98 or above, they'll assign themselves IP addresses that will work for this kind of thing
Finally, the primary logon should still be windows logon. Client for microsoft networks is only useful in an NT domain, In fact, if it is set to primary logon, it will either lock you out of your own machine, as it can't find the primary domain controller, or it will let anybody use your profile (but not your password list) just by entering the wrong password at the first prompt, and then pressing escape at the next. D'oh!