Inactive ihave a virus and my computer is running very slow

[Inactive] ihave a virus and my computer is running very slow

Hello, i have an XP and it is going very slow and I think it has viruses. I looked up some ways to stop the problems but I found nothing and it won't go away. I'm also having poP up problems in firefox and internet explorer and my computer is filled with files.I really need HELP with fixing these problems because everything I do doesn't work and I'm a newbie when dealing with computers. i tried everything in my power so please help me. I dont have enough memory space to run disk defrag.