I am going to make a dual boot system and i was wondering what linux distribution would offer new things that windows dosent. It would be nice if the distribution was free. I was also wondering how much i should partition off for linux

I am looking for Linux Distribution that is the best one for the avid Windows User that can be downloaded and installed directly on my computer. I do not know how to burn ISO files, plus I need something fast and easy.

Have decided to try out Linux as most of the applications I currently use are open source anyway. However, there are a myriad of different distributions to choose from. Which would give the best general overview of the Linux experience

Which linux distribution would be the best to install on a older computer that still woks fine, like: 866mhz, 512ram, 80GB hard drive?
I mean, so I can reuse an older computer for basic tasks such as browsing the web, writing documents, store some music and pictures.