Help!!! A virus has taken over my computer!! =[?

I have to ask this on my skool pc bcuz my one at home seems unusable...

I haven't downloaded ANYTHING supiscious recently however when I woke up this morning my computer was performing vERY slow. adds popped up saying "Download this spyware protection now" "Your PC is infected, do this now", etc. about 20 of them!!

The WEIRDEST thing is my desktop wallpaper changed to a red one with a malicious symbol in the center. I couldn't see all of it.

Please help if u can, thanks!!! =]

Help!!! A virus has taken over my computer!! =[?antivirus programs

Scan your computer for free with BitDefender's online virus scan. They are one of the leading anti-virus products and it will allow you to clean or remove the virus.

BitDefender Online Scanner is a fully functional antivirus product, but you will need to get an anti-virus program. If you want a free anti-virus I recommend in order of popularity, but please choose the right one for you (install only one):

1. AVG Free

a. A simple interface (easier to use than Avast! and Avira)

b. Can detect about 82.82% of viruses

Cons: low virus detection

2. Avast!

a. Real-time protection

b. It has an option to delete a virus once found

c. Can detect about 87.46% of viruses.

Cons: Too many icons and confusing user interface