OK - don't panic!!
Is this a new problem? i.e. has your computer previously recognised your iPad and now, suddenly, it doesn't?
Do you have the latest version of iTunes installed - at least iTunes 10.1?
When you say it 'isn't recognised' I'm assuming that you mean that, when you plug your iPad into your PC via the USB cable supplied with the iPad nothing at all happens - even if iTunes is already up and running?
Let us know and we'll see what we can do to help.
Tim