you need to install anti-virus software.
A free one is called "Comodo Antivirus"
But before you do that, restart your computer and as soon as it starts turning on
tap the letter F8 ontop keyboard one time every second, keep doing that untill you get to a screen
that lets you choose "safe mode with networking" the networking means "internet"
The reason you do that is so the virus wont work.
So download Comodo antivirus and do a full scanwhile in safe mode.
While its doing that, go into internet explorer add-ons and disable all of them.
Also in internet explorer options, make sure your home page is set to what you want it to be.
Then go into control panel and uninstall all the junk software you see.
But simply doing a virus scan should work fine.
After all that you can also try a new browser. I like Chrome or Mozilla firefox.