Open in your text editor C:\Windows\system32\drivers\etc\Hosts
file and add a comment hash # to every entry other than 127.0.0.1 localhost
Save the file and try your http://localhost
You may have to right click on Notepad and select run as administrator if you are using Vista.
Unless you have added other entries yourself then you only need the 127.0.0.1 localhost entry in the Hosts file.
Your adware may have added lines to the Hosts file as part of it's agenda and if your hosts file works now you have commented out the other entries then it is safe to delete those other entries except of course the 127.0.0.1 localhost entry.