The one I got was the "Google Redirect" .... this is caused by something called the 'TDL3 Rootkit' which causes the Google redirect virus infection. A person who is using Google as a home page or search engine is redirected to visiting unwanted websites ..... and its a real bugger to get rid of!!
Eventually after much searching (hampered greatly by the fact that I was being redirected) I found a site that didn't just spout nonsense .... "How to Remove the Google Redirect Virus", which apart from being full of generally good advice, has a specific link to the the utility 'TDSSKiller.exe' which is by Kaspersky, and killed the problem in a few moments ...... so a full cheer from a grateful web user for these companies who offer free cures for very nasty little problems.
Oddly, I still have no idea where I picked this problem up from because I most definitely did not give any administrator permissions to a download ..... ah well, at least its apparently fixed for now.
