While it takes a bit of concentrated effort to get all of the functionality of Windows (especially the multimedia aspects - Microsoft and Hollywood lawyers making open source software codecs almost a crime to produce), Linux makes old PCs stand up and howl.
I am a new convert to Linux and am learning to debug Linux installations. Once properly setup, running Linux is a breeze. I have three computers in the house and only one is running a Microsoft product (XP). I have no intention of installing MS 7 and will presson with Linux distributions in place of MS.
Linux on an older processor and with the kind of RAM that MS products require absolutely screams. If I were to purchase a new machine I would install Linux and not MS from the get go.
Running Linux Mint 8 64 bit here...on a black AMD 7850 with 4 Gig of memory and a 500 gig Seagate HDD and a nvidia low end graphic card...
Welcome to the *nix world.
Welcome to the clan.