The speed of your Internet connection and the speed of downloads may be affected by several factors including:
Viruses on your computer:
Viruses often slow your computer’s performances as they demand processing power and use Internet resources because they often send out massive amounts of information over your Internet connection.
Spyware on your computer:
Spyware, like viruses, often slows your computer’s performances because they demand processing power and use Internet resources. They often send out information over your Internet connection.
You may experience what seems like a slower connection as Internet use from your own home increases due to download of large files or multiple users on your home network accessing the Internet connection.
Be aware of file sharing software that might allow others to access and download large amounts of data from your computer. Any Peer to Peer (P2P) file sharing clients by default, will share your connection with others on the Internet. Consider configuring such programs to have uploads and sharing disabled.