It worked! I managed to move our whole office network within the day.
Move where you ask? from one IP range to another IP range. OK, that's only a software thing so I didn't use a single screwdriver, but the significance of a move is quite huge from my perspective.
Computers on a network each have an IP address, so that they all know where each other are. There are a whole bundle of addresses that can be used in private networks and originally i set our network up on the 192.168.1.??? range (where ??? was the number for each computer). Unfortunately I discovered that this is now a range commonly used for free wireless network access at hotels. If i was using that range in a hotel I wouldn't be able to VPN (virtual private network - a way of connecting to my office over the internet securely from anywhere else on the internet) into my office as the two ranges were identical.
The solution? Move the office network into a new range 10.x.x.??? - where the x's are two numbers i chose at random and would remember, and the ??? the number of each machine.
To begin with, all of our machines had an IP address that i set by hand when I first install them. To save having to do this on every machine in the future I decided to use DHCP (Dynamic Host Control Protocol if i remember correctly) which is common and often on routers (3 of our routers can be DHCP controllers, but you only need one on a network). I set this up to give out addresses in the old network space and went round every computer, printer and server to make it get it's IP address from the DHCP server. That took a couple of hours but at the end I could see that the router knew about every machine on our network.
Then, I changed the router to give out addresses in the new network and restarted every computer, printer and server. Checking the router again I could see that all the machines were known about on the new network.
Now the boring bit, I never gave our printers fully qualified host/domain names. If I had chosen to call them things like "laser.rkbb.co.uk" (i tend to use that domain for things inside the office because it is short) then all the PC's would have been able to print to them at their new address. As I hadn't done that, I had to go to every machine and manually change the printer settings to point at their new address. From this point on I might start giving every machine on our network a fully qualified domain name.
The bottom line: I moved the whole network in a day, and it worked. I do like it when computers work the way I expect them too :)