Peer-to-peer problems

I have three xp pro and 2 xp home computers on a peer-to-peer network.
Everything was working perfectly. I downloaded an HP Software update and the computer (xp home) I downloaded it on then couldn't access the network although other computers could access its files and it could access the internet. I uninstalled the update. Still couldn't access the network. I checked the firewall. Turned off. I reinstalled the network with the wizard. Still couldn't get on. I reinstalled the lan components (file sharing, microsoft client net, etc.) still couldn't get on. I took everything out of the startup msconfig menu ... no help. When I go to the computer properties, the name is correct, the network name is correct. Called HP support ... they don't support network problems. I had no network problems until their download. I have removed their software update program and all the updates. Still can't access the network, tho the network can access this computer's files. My settings do not fix the ip addresses but rather let them choose an ip address. It has always worked that way before. HP wants me to choose fixed addresses. Is there anything else I can do before I do that?
It always worked before. I have disabled all firewalls and virus programs. This is a simple network. What could be wrong?

Please help.

 

I am also able to ping other computers from the computer that can't see the network. When I try to see the computers in my workgroup, I get the message "Workgroup is not accessible. You may not have permission to use this network resource. "

 

Sorry I didn't hear anything from any of you, but thought I would let you know how the problem resolved itself.

I finally decided to check the router ... there was a box sitting on top of it, causing it to overheat. I unplugged it and plugged it back in (with the box off of the top of it) but that wasn't enough. I also had to unplug and replug each of the connections to the computers themselves. That did it. Too bad the error message couldn't have said "You've got something on top of the router, stupid ", instead of "The network is unavailable. You may not have permission etc. etc. contact your administrator (me) etc. etc.

Oh well. Now I will put "check router" in my network error book.