because i got a big warning on my computer saying that i have a virus,and than i try to running window defender and it wont let me do it.and it's scanning my computer with something that pop up with the virus warning, and it's telling me that it will remove that virus if i sign up for some virus protection and also asking me for my credit card. The virus wont let me get on the intrenet,so how can i download a free scan on my computer ,can i download it from safe mode and it's safe to download it from safe mode.