Why is my internet really slow all of the sudden?

my internet started slowing down a little bit about 2 days ago

and my downloading speed is really slow i think i have a problem with my network but i dont know what to do

my downloading speed used to be 400 kb/s now its never above 40 kb/s

i dont think i have spyware i have done full system scans with Spyboy S%26D, Windows Defender, Ad-Aware 2007, SmitFraudFix, RogueRemover Free, and Avast Antivirus 4.7 Professional

Why is my internet really slow all of the sudden?best antivirus software

Lots of possibilities... first we need to know how you're using your network, what you're downloading, who your provider is, etc. Also, what kind of/how old is your computer? Memory, etc.?

For example, are you using BitTorrent to download? Comcast has recently begun interfering with BitTorrent downloads by sending a disconnect request to each end of the connection, pretending that each request came from the other end. Class action suits have started in at least two states.

Another possibility... when was the last time you rebooted your router and/or cable/dsl modem? Many routers, especially anything older than a year or two, have trouble handling a lot of simultaneous connections. This can be a problem if you're downloading with eMule, BitTorrent, or, if the router is old enough, just a lot of plain 'ol downloads. Once the router starts to go under, speeds drop, connections are slow, and the only fix is a reboot of the router.