Possibly a
rootkit, some of which can be quite difficult to remove, with varying levels of danger. You should seek help at one of the many online forums that have highly trained & skilled volunteers who will guide you through the disinfection process, or failing that, will help you in reformatting your box.
Here's 2 sites I like:
Geeks to Go! Virus, Spyware and Trojan Removalhttp://www.bleepingcomputer.com/forums/forum103.html">BleepingComputer.com > Security > Am I infected? What do I do?
Make sure that if you decide to start a thread at either of these--or any other sites you may find-- that you read the instructions on forum rules, how to's & any prep you may need to do before posting a thread.
Do you have any Anti-Virus or Anti-Malware programs installed?
Try downloading
SUPERAntiSpyware Free or
Malwarebytes Anti-Malware FREE {I have both on my machine) and run a scan. Malwarebytes will scan much quicker than SUPERAnti, but SASW is more thorough, IMO.
Don't be surprised, however, if these programs or any others you may already have installed, are BLOCKED from running, or run for a few seconds and terminate for no reason, or if the THING you have inside your machine blocks you from even going to any malware removal related websites, there are ways to get around that, but I'm not NEARLY knowledgeable enough to instruct you how-to.
Give either, or both of the programs I mentioned a shot---they may find enough Malware to at least make your machine operable. Even if these programs help, I would suggest going to one the many online forums that deal with these kinds of problems. There's more than likely some sort of evil still lurking, if it can be removed, the tech's there will find it with their many specialized tools and programs.
Let me know what happens, I may be of some help. I went through a similar problem about a month ago--Searches re-directing, error messages galore upon bootup, annoying pop-ups for
ROGUE VIRUS REMOVAL PROGRAMS...