You probably have too many programs automatically loading at start up.
This tells you how to disable them - it's easier than it appears but PLEASE only disable programs you know your pc doesn't need to run, such as Skype, printer. If you're not sure, leave it alone or ask on AB
http://www.howtogeek.com/74523/how-to-disable-startup-programs-in-windows/
The speed of your downloads can be two things - slow internet connection or a browser made sluggish by conflicting add ons and extensions. What browser do you use?
I am unsure about deleting the windows.old although I have done it without problem. It is a different matter telling someone else to do it, though, in case it all goes wrong.