Spyware and virus problems!! PLEASE HELP?!?!?!??!?

I have a Toshiba Laptop and one time when I was doing my homework, randomly a scanner popped up that I had no idea that i had. It said i had spyware and viruses and that i have 38 items infected. My desktop background is a big blue message saying i have spyware and that i need to delete it as soon as possible. But when i searched "spyware" in the start menu, i found a spyware and virus detector and i did a quick scan and it said my laptop was fine and it said it was running normally. but its NOT!! my internet is running extremely slow and sims 3 and skype wont work! it says i dont nhave the correct permission to access this item. whats going on?? please help, is there some donwload i could use to delete these viruses and spyware for free?