To get back to where it was new you can restore to the factory load. I find most folk do not want to dive into tools, uninstall apps and more today.
That's why, in your case you may want to consider a tablet where you don't fuss with this.
I've been reading all the complaints on MS OS's filling up hard drives but as I am not an IT specialist I am at a loss at how to stop it or clear my own C drive for more space. I constantly do all the normal things: disk cleanup, defrag, etc. I only have a few MB left of a 40GB partition and every time I delete unwanted files Vista downloads updates and fills it back up. I hardly have any applications left on the machine and the computer is becoming worthless!!
There has to be a simple solution that Microsoft can provide without making you pull your hair out! If there isn't, they better start saying goodbye to any customers they still have.