I've downloaded many files with several breaks in the streaming (fraction of a second interupptions) and wonder what can be done to reduce them, besides the usual: use 4 star files, bitrate of at least 128, reload again.
I use DSL, Windows XP, fairly new computer

Also, some files have a hum or hiss in background, like old vinyl records. What causes this?

If a computer really slows down in loading could one reson be too many files? Is the solution to delete some files in the Library or could it be a virus slowing things down?