You should tell your NW administrator before installing it, because you will need an ip address for your ubuntu OS, (although if you don’t use DHCP, you could use the same static ip address you use in XP).
Your user account does not need any changes.
If you want to dual boot, you will need a separate partition for the Ubuntu installation. If you don’t have such partition, there are some tools you can download, which could help you resizing your current partition, so you don’t need to re-install your current OS nor re-format your disk.
Have a look at this article for detailed instructions.