How can i get rid of a virus?

something similar happened to me except it was everything wanted to open with Mozilla Firefox but all i did was restart my computer and ran system repair if you can't figure out how to run system repair i would just Google it. mine had it as recommended when i restarted my computer. if this doesn't work and if you run a virus scan and it dose not do anything then i guess your best choice would be to reformat your computer.