XP Home networking

Here's the equipment:

1-yr old HP desktop WinXP SP2 (machine name = PC1)
Brand new Dell desktop WinXP SP2 (machine name = PC2)
Workgroup name = "OFFICE"
All windows updates done on both

Linksys Wireless G router w/ 4 port switch. HP is cabled to router, Dell is wireless to it - about 8 ft from router to USB network connection. The PCs receive IP via DHCP from the Linksys router.

My friends have a plumbing/heating business out of their home. They originally had just the HP desktop. They recently moved to a new home with a larger "office area", so they bought another PC - so they can each work on invoices, Quickbooks, etc....

The HP originally logged in automatically as "Administrator" - there were no other User Accounts listed, except for Guest, which is disabled. When I set up their new Dell, I had to create a user account, called "Brenda" - which is an Administrator account. I ran the network setup utility on the Dell, and shared the new printer, plus Brenda's shared documents. I then went to the HP, and shared the same items (printer and documents).

So here I'm thinking, "Piece of Cake! Standard Home Network" right?? Here's where I'm totally confused..... the HP can connect to the Dell with no problems, can print and open shared files. The Dell cannot connect whatsoever to the HP. I thought it was a security issue, with the HP not recognizing the username on the Dell, so I created a matching username on the HP. So now when the HP is logged in as "Brenda", it can still connect to the Dell, but not vice versa.

Both PCs can connect fine to the Internet. Both can connect to the router via browser. Oh, and from the Dell I cannot PING the HP system. Somebody mentioned using NetBEUI on both, so I installed that (in addition to TCP/IP) but that didn't do any good either.

Ideas? I'd really love to get this fixed for them soon - Please help!

Thanks!

disable the firewall on both then see where you are at.

I disabled the firewall on both, and still could not access the HP from the Dell. Finally, I unplugged the USB wireless network connection, and ran a CAT 5 cable across the floor to the router. I was instantly able to connect to the HP from the Dell. Removed the cable, and plugged the wireless in again.... nothing....

I have troubleshot the wireless setup - reset the router to defaults, changed SSID, toggled frequency, etc... but then I think of how the HP can always connect to the Dell, just not vice versa....

For now, they're content with a cable. They put a rubber roadbump over it so they won't trip on it. I borrowed the wireless adapter and took it home to see if I can duplicate the issue. I haven't had the chance to mess with it yet.

**BRAINSTORM**
Early last fall, these guys called me in a panic state because they thought their HP had crashed. They said they reloaded XP, but when I got there, all the programs were still installed but I had to re-install them to make them work. Is it possible they reloaded over the top of the existing install, thus hosing up the XP security? Up to that point, they has antivirus installed and updated, but they'd never done an SP update nor windows updates. I spent most of the day reinstalling their programs and getting Windows updates.
Just a thought.... :-)