Short bio: Computer Scientist, FOSS supporter (read more)
Tux Machines (TM)-specific
Windows is great, but after a while, it can get cluttered up with too many programs and become intolerably sluggish. Backing up your files and reinstalling it can help, but an alternative is to try the free Ubuntu operating system. Ubuntu isn't too demanding and can make even a lowly netbook seem sprightly compared with running Windows on it.
Ubuntu is one of many Linux distributions, but it's arguably the most polished, most compatible and best supported (around 20 million people use it on a daily basis). The latest version, discounting beta releases, is 11.10 Desktop Edition. This is a one-size-fits-all version which will run on anything from a humble netbook to a top-end desktop PC with multiple monitors.