How do I get my htttp:://www back?

My computer picked up a nasty virus which hid my ZoneAlarm from view (we thought it had removed it) and also locked us from internet access so I purchased another anti-virus software (PC something or other) and one of the things it did was force me to update the Microsoft software. Before I made this change, when it came to type in a url in the browser, I could simply type in the name, like democraticunderground and it would immediately take me here to DU, but now I get an error message because it expects me to fill in the full url, or at least, "www" before every address. So, how do I customize the browser so that it will automatically put in the http, etc on its own?

...to the Microsoft site:

http://www.microsoft.com/downloads/details.aspx?FamilyID=9ae91ebe-3385-447c-8a30-081805b2f90b&displaylang=en

...and download the new browser OR

Go to Start, Run and type in SFC /runnow

Have your Windows disk ready and the Above will scan your system and fix any system files that are corrupted.