win 7 and your PC are Fine
the problem is the slow speed of the DSL
nothing you disable, will help, unless it is some background process , sending data to the cloud for storage
nothing else is going to eat into your data bandwidth
IF you are watching youtube videos
there are several download addons that you can use
that will download the selected video to your PC, then you watch it with NO interruptions or buffering after it has downloaded
if you are trying to watch netflix etc..the best you can do is set netflix to SD resolution