If you click on the 'history' icon on the top toolbar ( it looks like a clock with an arrow going anti-clockwise) it will give you a list of sites visited today, Monday, last week etc. Right click on the one you want to get rid of then click 'delete'.
I haven't figured out how to get rid of the drop down menu from the www address bit. (if anyone else knows, I'd be interested!)
Try downloading 'Ccleaner' (yes two c's) from download.com or similar, it is free and once you set it up and save your preferences it will wipe all traces of history from your computer including autocomplete when filling in forms, you just run Ccleaner after each session on the net. It is also safer and more secure as it wipes all traces of bank details from your p.c. that you have used for transactions over the web.
if you have google toolbar, click on the coloured word 'google' on the left, small drop down window appears, then click 'clear search history, this wipes out your previously visited sites.
to clear drop down history from the address bar.
start>>>
control panel>>>
internet options>>>
clear history ( box about 1/3rd up the box that is displayed)