How to install

I am not aware of a way of installing Ubuntu on a NTFS partition. You should either delete it or resize it and make place for a Linux partition (ex. ext3).
If you used Windows on that computer have a look at https://help.ubuntu.com/7.04/windows/C/ it would help you with the migration.

https://help.ubuntu.com/community/GraphicalInstall shows you the steps of the installer (including the partitioning part).

Your computer's specification look quite OK, Ubuntu should work without a problem on it. Buying some more RAM will help improve the system (256MB is not much, try to get 512MB or more).

You might to check out Wubi (http://wubi-installer.org/faq.php). I don't know much about it or if it actually installs on an NTFS partition but it does install from within windows.

As for partitioning, you don't have to do anything before installing. The Ubuntu installer will do the partitioning for you. You only have to specify how much of your drive you want to give to Ubuntu. Be sure to read the options carefully on the partitioning part. A wrong choice could end erasing windows. Always back up anything you are unwilling to lose.

I don't think you'll have much success installing ubuntu onto NTFS formatted partition, in fact I am 99.9999% sure it wont happen. What you should do is either format and create two separate partitions, or if you dont want to reinstall windows etc etc, resize your existing partition using a tool such as Gparted or Partition Magic, or any other partition resize tool, and then install ubuntu onto the newly allocated free space.

Obviously if you are going down the route of a partition resize, do a full defrag (or two).

Install windows first if you go down the format route, that way ubuntu's boot-loader will detect the windows installation and create a boot-entry for it. Installing ubuntu first makes life harder because windows will overwrite the ability to boot Ubuntu (by rewriting the MBR and not caring about ubuntu).

Ubuntu will run fine on your hardware, generally speaking if you can tolerate windows on your specs, linux will run well. Of course, I'd be looking at getting to at the very least 512MB ram standard for any computer use, but either way you will be ok.

As far as supporting the printer/scanner/copier, it's not 100% guaranteed, it depends whether a driver exists for all features, like the scanning functions etc. Printing you will probably get to work, but thats a whole separate question. If your new to Ubuntu, install and have a play and over time you will figure out all the intricacies.