Well,
A. i don't know what this boards thoughts are on answering questions on piracy, Since bittorrent files are 99 out of 100 used to transport "warez" on.
B. Spyware, cannot be found in movies, mp3 and picture files. There is no way as of yet, to put spyware into those mediums.
To get spyware in your system you have you either have to accept it online via a website, or have it installed into your system. The thing about spyware is that it is legal, meaning somewhere you said it was ok for it to be in your system. So if you install a program that has spyware in the Eula (End User License Agreement) It will say it somewhere in there, that it will install "insert name here", when you choose to agree to all terms of the Eula. Most people would skip through the 10 pages of legal "mumbo jumbo" on it, they rely on this to screw you into getting it onto their system.
Basically put, spyware would have nothing to do with your downloads being slower, unless they were installed onto your system and your on a 56k or something......
Do you even really understand how the bittorrent protocol works?
Read this, though i doubt you would understand what it means. The idea is the more people with the file, the faster your download speed will be. So you must be downloading files, that are not in alot of hands. From reading around everyone is now hooked to exeem which is a napsterized version of bitorrent. So maybe your downloading from sites that are about dead now, since that came out.