If you use things like Utorrent (and there are plenty of legit reasons to use some torrents -- Linux distros, Driver packs etc) then DO NOT UPDATE to the latest version of Utorrent.
What it does --even if you don't want the toolbar installed -- adds an "Addon" to IE10 which changes your home page --and it's the devil's own job to undo or get rid of this even if you totally uninstall Utorrent. You can disable the add on but the REMOVE option gets greyed out --also a NO NO in my book.
Fast Solutions: How To Remove uTorrent Toolbar - Fast Solution
This solution "sort of works" but you probably are better off restoring a previous image of your system.
The "Naughty file" is prxtbuTor.dll although it's not actually a Trojan or virus --just handles the toolbar etc stuff.
prxtbutor.dll - What is prxtbutor.dll ?
Some sort of file from Conduit ltd (conduit toolbar).
Utorrent WAS fine -- I don't like "customized toolbars" and I HATE anything that interferes with my default HOME page.
So any utorrent users --DO NOT UPGRADE.