How does a list of old downloads have ANY impact at all on the rate at which you download new files? If that's an indication of the kind of tips this "Insider Secret" site or whatever is offering up, then they are completely full of it. That has got to be one of the single dumbest "tips" I have ever heard someone offer up. And while I get that you're just repeating what you heard, you might want to apply a slightly tougher litmus test to the things you believe from places like that. Remember that pretty much anyone with $200 or so to spend can throw up a very professional looking website in an afternoon. It doesn't mean the content contained in the site is worth anything. Look at Wikipedia for example. I know next to nothing about neuroscience, but I could certainly go and edit the Wikipedia page on neuroscience if I wanted to. Make all kinds of outrageous claims either pro or con, with absolutely nothing to back them up.
Tips for improving computer performance are like old folk remedies. There's hundreds of them out there, and the vast majority of them are completely and utterly useless. In fact, when you stop to think about them for even a second, they're so completely obvious you feel like smacking yourself for being so stupid as to believe it even for a moment. The idea that removing a list of previous downloads will somehow improve the speed of future downloads should be in that category.
And I'll say again... If this is a representative sample of the "tips" offered by this site or whatever Insider Secret is, then they have wrestled away the crown from the worst "tech" information source known to me. Given the former holder of this distinction is an unnamed company that has a red circular logo with a big white C inside it, that's quite the accomplishment. Not one to be proud of though. Find yourself another source for "tips". Or better yet, don't rely on tip sites, but read forums and mailing lists. Every now and then someone will inadvertently describe how they do something, and it will be a better method of how you perform the same task. Tip sites, as a general rule, don't have any actual tips, just useless and erroneous suggestions.