A little bit about blackle.com. I would add a rider to anyone not to go direct to the website as I have doubts similar to methyls.
http://en.wikipedia.org/wiki/Blackle
It would appear that 'Blackle' makes fundamental changes to Internet Explorer which are not easily reversed. I suspect some of them to include Registry changes.
I don't see an easy way out of this other than a re-install of Windows 7. Just before you do though try a scan with Malwarebytes (free version) and CCleaner and remove anything vaguely connected with 'Blackle.
I'd also empty your 'favorites' folder located at C:/Users/'your name'/favorites
Personally I don't use IE at all, preferring Firefox myself. I do have IE 11 installed which appears to work ok when I use it.