You've managed to pick up a malware program ( I suspect you've clicked a link for video and you've been asked to download some .exe program to allow the video).
Start up your computer in safe mode with networking. (tap F8 key whilst windows is starting up, till you get startup options screen) select safe mode with networking)
Once started, open your web browser and search for Malwarebytes Anti Malware (MBaM)
Download and install MBaM, then update MBaM.
Run a full scan using MBaM. It should find the malware that's affecting your computer. Once the scan is complete, remove the items it finds (fairly obvious what to do)
Restart your computer in normal mode.
Once your computer has restarted, you'll have to turn off System Restore and then create a new system restore point from today.
(Do a search on the internet for how to turn off and turn on system restore)
It's most important that you turn of and turn back on system restore though, because if you don't, then you could unwittingly restore your computer (at some time in the future) back to a point where your computer was infected.
I had the MS Removal Tool Malware about a week ago. Took a couple of hours to remove it.
DONT whatever you do at the moment PAY ANYTHING over the internet for programs to remove whatever it is your computer says it has got. (specially if you get a popup telling you, that you have a virus etc.
Anyways, loads of info on the net about malware infections and how to remove them.
Do let us know how you get on though, and I hope happy days are soon restored to your computer..