Disable all firewalls for testing.  This includes Zone Alarm, Norton Internet Security, etc.
    Including XP's ICF...
    From Control Panel, open Network Connections.
    Right-click Local Area Network from Control Panel's Network Connections and choose Properties
    Click the Advanced tab and deselect (remove the checkbox from) "Protect my computer..."
    Click OK and close out of Network Connections & Control Panel

Enable NetBIOS over TCP/IP:
    XP utilizes DNS for communication by default.  To enable the systems to communicate via NetBIOS,
    proceed as above to enter Network Connections.
    Right-click your Local Area Connection and click Properties
    Scroll down in "This connection uses the following items:" to find Internet Protocol (TCP/IP)
    Select it (highlight it) and click properties
    Click the Advanced button on the General tab.
    Click the WINS tab.
    Under NetBIOS setting heading
     Click Enable NetBIOS over TCP/IP
    Click OK, OK, OK and close out of Network Connections & Control Panel

Disable Simple File Sharing:
    Right-click the Start button and click Explore
    Click Tools then Click Folder Options
    Click the View tab
    At the bottom of the Advanced Settings list, deselect (remove the checkbox from):
     "Use simple file sharing (Recommended)"
    Click OK

Let Everyone's permissions apply to anonymous users as well:
     Click Start
     Click Run
     In the Open box type SECPOL.MSC /S <ENTER>
     Navigate to Local Policies/Security Options.
     Double click "Network Access:Let Everyone permissions apply to anonymous users"
     Click Enabled and click OK
     http://support.microsoft.com/?scid=kb;en-us;318030

Test your connectivity:
    Click Start
    Click Run
    In the Open box that appears, type CMD <ENTER>
    At the prompt that appears, type IPCONFIG <ENTER>
    Do you have an IP address listed (192.168.1.100)?
    If so, try pinging the other machines by IP address:
      PING 192.168.1.100
    If you get a Reply successful, then try connecting to them...
      NET USE * \\192.168.1.1001\C$ /USER:192.168.1.100\Administrator Password
    (where Administrator is an administrative account on the machine you're trying to get to)
    (and where Password is the appropriate password for that account).

I followed every step you gave - these are very good instructions . . .
On the "test your connectivity" instructions,  the ping the other machines works fine. Zero errors.

But when I use the NET USE command I get:
"System error 53 has occured.  The network path was not found."  

I followed your syntax carefully - wasn't sure of ending - so here is what I used when I tried to access Julie's computer from Amber's computer:
NET USE * \\192.168.1.1001\C$ /USER:192.168.1.100\JULIE jw$323#tw

I also tried our Administrator user name and the server sytem password - no luck.

When I go to explorer and My Network Places I can browse to our regular in-office domain name and open up the domain and see the 2 laptop computers.  Only the 2 computers that I'm trying to link show up - which is right, because these 2 are not connected to any other network system.

But when I double click on the other laptop's icon, I get:
"\\Julie is not accessible.  You might not have permission to use this network resource. Contact the administrator of this server to find out if you have access persmissions. There are currently no logon servers available to service the logon request."

I get the same message from the other computer -except Amber's name is in the user spot on the start of the message.

Thanks for your help so far . . .

Yikes!
    NET USE * \\192.168.1.1001\C$ /USER:192.168.1.100\Administrator Password
should be
    NET USE * \\192.168.1.100\C$ /USER:192.168.1.100\Administrator Password
Note the missing "1"..............^

So, yours should read:

NET USE * \\192.168.1.100\C$ /USER:192.168.1.100\JULIE jw$323#tw

However, make sure I'm clear here:
All 3 laptops are part of the same domain, I'll call it DomainA.
In the office, on DomainA, everything works fine.
You head out to a client's site.  They potentially have either a workgroup or domain on site (DomainB).
Now, you don't necessarily want anything from DomainB, just have the 3 laptops share data between each other?

Without DomainA to validate your user account, you'll need accounts set up on each of these machines.
Julie's laptop: Laptop1 will need 'local' user accounts Amber & Stacy
Amber's laptop: Laptop2 will need 'local' user accounts Julie & Stacy
Stacy's labptop: Laptop3 will need 'local' user accounts Julie & Amber

Do you have them set up this way?
Click Start->Run->control userpasswords2 to add user accounts...

OOOOO kayyyyyy . . . .   now it's starting to make sense.  
The syntax with the NET USE wouldn't have been the real problem - it was my ignorance of the Domain issue.  No,  I hadn't set up a new domain for the laptops when they are out in the field.  I was still using the regular in-office domain.

I'll give this a try as soon as I can get the laptops together again (Saturday) and I'll bet everything will fly.  Let you know by next week.

Wow - thanks - seems like this should be easily described in the Linksys instructions . . .  maybe it's too elementary - and I'm suppose to know it - ha.

Thought I could figure out the domain thing - but alas . . . no luck. Now I'm really cofused.

What I have.
Just 2 XP notebooks,  Julie and Amber.
Each now with a PCI wireless G card.
Each have the card configured for an adhoc network  G, channel 6 setup.
Each wireless connection shows "enabled" - and running fine - good signal.
Each has the other person setup as a user with Standard permissions.
Each has the drive C shared as C$.

But I still can't see the other's C drive  . . .

Now on Julie's I need to put ?
NET USE * \\192.168.1.100\C$ /USER:192.168.1.100\AMBER ag$323&sb
and on Amber's put ?
NET USE * \\192.168.1.100\C$ /USER:192.168.1.100\JULIE jw$323#tw

I try these but I get "don't have permissions" messages.
 
Any thing wrong?
If I would get it right - won't I be able to access the other's C drive - through explorer? Through My Network Places - or where?