Many thanks to all who helped with my wallpaper problem. Another website - help2go.com said the problem was a "warnhp.html" caused by the Spyjack f trojan. Have used numerous programs to no avail but what they suggested seems to have solved the problem although I am more with the idea that it has gone into hiding instead of just being gone.
With that out of the way, my laptop now will not turn itself off. It will go through all the motions until finally it displays the screen "Windows is shutting down" and then stay like that quite happily. There is no indication of the hard drive doing anything at all. It will just sit there in mute silence. Ultimately I have to disconnect the battery for the thing to shut down at all. Not the best way I'm sure but the only way available to me at the moment.
I would greatly appreciate any help in this matter. And again, thanks for your help before.
While you check out the links supplied by Fruit Bat /\0/\, might I suggest that in the meantime, instead of removing the battery or PSU lead, you hold the power button down for approx 5 seconds and it should switch off, what you are currently doing is not entirely without risk.