4.2.2.1

One day as we were trying to network two laptops (both XP) together for file transfer, one of the guys told us to set our DNS servers to 4.2.2.1 so that they would query the network for the hostnames.

Google'ing, I can't find anything explaining the use of that IP address. Could someone please point me towards the RFC or other documentation that describes it?

I'm not sure who mentioned 4.2.2.1 as the IP address you need for file transfer. How are you trying to connect them? Through a network using a router, or directly from one computer to another?

It was a direct computer-to-computer connection with a cross-over cable. But XP security seemed to keep getting in the way.

4.2.2.1 was given to us as the DNS Server address to set up in our own private little impromptu LAN. I've used it at home between my XP and ME laptops, after removing the ME's name from HOSTS, and it seemed to work. I'd just like to understand how and where I can research more on it.

Ahh.. well this would be better suited for the Networking forum. I'll ask a mod to move this for you as you will receive better answers over there.

4.2.2.1 is the IP address for Verizon owned DNS servers. You should only use that IP for your DNS server if you're a Verizon customer. Your ISP will provide you with the IP address of their DNS server. If you're not Internet connected your network will need an internal DNS server if you want internal name resolution.

DNS is not needed at all for file sharing, Secondly if you are not connected to the internet 4.2.2.1 wold not be rechable to even query, Thirdly I highly doubt that 4.2.2.1 has your computers "A" records on it to serve any purpose in name resolution between your computers even if you could talk to it.
I think you got hornswaggled.

4.2.2.1 is one of the primary dns servers on the net, in fact it has a reputation for being one of the fastest servers; i always use 4.2.2.1 as my dns server, and 4.2.2.2 and the secondary; if you use your local dns server, it can only find what's in cache, if not, if will usually route the query to the isp dns server, if it cant find it it will route to one of the primary dns servers, with 4.2.2.1 being one of them, i could be mistaken, but i think it is the first root dns server on the net

No, 4.2.2.1 is a DNS server owned by Verizon for their customers (which includes me), and it's not a root server. So if you're not a Verizon customer you are at a minimum being "rude" by using someone else's DNS server without paying for the privilege, and you may be part of the reason I sometimes see slower DNS resolutions

Actually, this "server" is a set of servers in each of the following datacenters: Chantilly VA, San Jose CA, Cambridge MA, & Phoenix AZ (I believe the Phoenix ones have be decommissioned)

I can't tell you exactly when they were built, but they were originally darpa servers, and have been rebuilt over the years. (last time I saw them rebuilt was on sun hardware back in 1999)
BBn became Gtei, Gtei became Genuity, Genuity's datacenters were seized by Verizon, Verizon sold off everything to Level 3, level 3 then resold everything back to either Verizon or CSC.

Only reason I know this is becuase i worked there (still do)
you'd be amazed at some of the ooooold servers out there that people still rely on. We were told when those servers went to verizon that they would be shut down/used for internal use only. Im really surprised to see them still in existence today and deliver the fastest lookups around.

basically.. use them.. keep using them, they are the best and as far as we know, the original root servers out there.