With Skype and Chrome open, my laptop runs at 6% CPU (i3 2370 2.4GHZ) and 20% RAM (8 gigs I think it's GSkill, 2 sticks of 4 gig).
That is
you. Again, understand that your computer is not equal to that of others, and different people have different needs.
A fresh install of Windows will get rid of all things not required to make Windows run (unless you have a laptop that came with bloatware, there is a option to install Windows only). This will lower your resource usage down to the minimum for the operating system.
That's the thing, for me, it's easier and a much more fitting solution for myself to just install linux than it is to back everything up and reinstall windows. Not only is it way faster, way smaller, and it uses significantly less resources and is incredibly customizable, it has a lot of nice quirks about it that I like, such as the bash scripting language, the ease of being able to compile pretty much any program from source, and a lot of developer-oriented programs and languages like lua, python, c and others being natively supported by the operating system. Most programs not available for linux can be ran through wine.
Why bother trying to make windows 7 work better, when linux already does that out of the box? It just had too many problems for me to use, and linux's benefits outweighed the cons. I'm not going to switch back because it works fine for you; it's my computer, not yours.
Yes, you're going to hit a limit of how low you can push the percentage, but as you said you're not going to need but 50% of your RAM anyway.
Your system can significantly slow down if your RAM or CPU usage goes too high. Once it gets to 80% or 90%, even your mouse cursor will start flipping out. 75% is within the safe zone, but carelessness can change that right away.