I have been in the position of having no desktop for the last 5 years. About 6 months ago I bought Steph a laptop as well as my own machie. I recently decided it was time to upgradeand having looked at the options came to this conclusion. To get a new laptop of the same spec as my old one would have cost me £2500

I bought a desktop which has a much higher spec for £1000. (HP Pavillion Elite m9180 uk-a) this included a LG 22" flatron monitor which is better for editing photos than a laptop.A lot depends on what you use it for, my intention is to get into the depths of photoshop CS3 which needs power a good CPU and plenty of RAM. Also the desktop has 3 500gb hard drives 2 internal and one external which slots into a drive bay. All in all the desktop exceeds my expectations.
BUT and it's a big but if you are using the pooter for internet access and the odd letter and photo then a mid range laptop is great about £400-£500. Personally I would avoid the bottom end £200-£300 machines. Hope this helps you decide John.