The bar which says 'Extracting - this may take a while' has now been going on for more than an hour. Is this normal and if not what shouldI do?
It may stay extracting for quite some time depending on where you choose to download the install files too. If you chose a location that the Adobe Download Assistant does not have permission to write too it will never leave the extracting state.
I would recommend canceling the download and trying again. Please choose the default location of your User folder to download the install files too.