I was working on some accounts today on my Win7 machine and having to do a fair bit of messing about - moving/deleting stuff - when the task bar along the bottom of the screen suddenly moved to be vertically up the left hand side of the screen

I need it to lie back along the bottom again !!

Can anyone please advise me of a simple way to achieve this

This should work:
Click a blank portion of the taskbar.
Hold down the primary mouse button, and then drag the mouse pointer to the place on the screen where you want the taskbar.

OR look here

here

Thank you SO much, Winfrey !! Your instructions worked perfectly

Seems like you should "lock the taskbar" when you get it where you want it so it doesn't accidentally go wandering again.

OK. I've clicked on "Lock theTask bar". Is that all I need to do ??

[ Never had one suddenly move like that before on any of my machines ]

Yes I think that will hold it in place as long as the "Lock the Taskbar" is checked.

Thank you very much