George,

Accessing the internet and sharing files on your LAN are two separate processes,
with different abilities and restrictions.  And require different network
components.

File sharing uses the processes of authentication and authorisation, and
requires both processes to be successful before you can share files.

Are you running both Client for Microsoft Networks, and File and Printer Sharing
for Microsoft Networks (Local Area Connection - Properties), on each computer?
Do you have shares setup on each?

Are you running NetBIOS Over TCP/IP (Local Area Connection - Properties - TCP/IP
- Properties - Advanced - WINS) on each computer?

Make sure the browser service is running on each computer.  Control Panel -
Administrative Tools - Services.  Verify that the Computer Browser, and the
TCP/IP NetBIOS Helper, services both show with Status = Started.

On any XP Pro computer, check to see if Simple File Sharing (Control Panel -
Folder Options - View - Advanced settings) is enabled or disabled.  With WinXP
Pro on the LAN with Win2K, you need to have SFS disabled.

With XP Pro, and SFS disabled, check the Local Security Policy (Control Panel -
Administrative Tools).  Under Local Policies - Security Options, look at
"Network access: Sharing and security model", and ensure it's set to "Classic -
local users authenticate as themselves".

With XP Pro, and SFS disabled, if you set the above Local Security Policy to
"Guest only", enable the Guest account, using Start - Run - "cmd" - type "net
user guest /active:yes" in the command window.  If "Classic", setup and use a
common non-Guest account on all computers.  Whichever account is used, give it
an identical, non-blank password on all computers.

More about file sharing, between all different versions of Windows:
<http://www.microsoft.com/downloads/details.aspx?FamilyID=87c0a6db-aef8-4bef-925e
-7ac9be791028&DisplayLang=en>

Cheers,
Chuck
Paranoia comes from experience - and is not necessarily a bad thing.

I don't know much about zone alarm, but are you allowing
the following ports

tcp 139 & 445
udp 137 & 138