Update

There is software update available for my ipad, however on downloading, it does not update my OS.

What is your current OS version? Are you attempting this update through iTunes?

My current OS version is 4.2.1. Yes I am trying to download the software update for my iPad- via iTunes.

I updated mine a few weeks ago, so my memory is quickly fading. I recall, in general, that it was pretty painless and intuitive.
Do you have the latest version of iTunes? I recall that this was necessary.
iPad is plugged in via USB?
I notice a procedure here:
[Moderator edit: Removed reference to external iPad-related site. Please, read the forum rules. Thanks.]
Hopefully, following this process solves your problems.

Try reading through this thread. Lot of explanations and troubleshooting tips.

http://www.ipadforums.net/ipad-help/...eshooting.html