Do you need the computer to be portable and move between each room, outside, round a friends, in your car?
Laptops are great and can easily replace a desktop for browsing, office, lighter gaming and heavier (if you get a top end laptop) CD-R, DVD-R burning etc. Come right down and price £600 can get you a decent laptop. I have a laptop and coming from desktop laptops are a lot more enjoyable to use (sit in bed whilst playing doom, watching a movie etc)