If it were me in this situation I'd be looking at what I could keep from the desktop and budgeting for the new parts, but that depends on being able to reuse the PSU, monitor and hard drive. I'm guessing the optical drive is fine, too. I'm sure you could get a motherboard, an i5 2500K, a reasonable graphics card and 8GB of DDR3 1600MHz for the same as that laptop, and even if it is a little more you'll be futureproofing yourself to an extent with the 2500K (because it's easily overclocked), whereas the laptop processor is a third slower, and if you came into possession of, say, £1,000, and you wanted to waste it on your PC, if you had a desktop already you could buy two high-end graphics cards and a decent PSU, whereas if you don't already have the desktop you have to buy one first.
That's just how I look at it. Then again you might actually want a laptop for it's mobility, in which case what do I know? My laptop doesn't even have a functioning battery in it.