Sounds real nasty, probably ran a booby trapped executable which turned out to be a trojan. Personally I've never come across anything like this but the first thing I would do is try to run Malwarebytes Anti-Malware. Depending on how aggressive whatever you have is you may not be able to run it. Best thing to do would be to grab Chameleon which is designed to force MBAM to be installed:
Download Chameleon from the link above. Unzip the contents to a folder in a convenient location.
Follow the instructions in the included CHM Help File or, if the help file will not open, simply try to run the files by double-clicking on them one by one until one of them remains open, then follow the onscreen instructions