Anyway... on a more serious note.

Are you looking to replace the 2.5" HD inside the laptop? If so you will have to pay slightly more than a standard 3.5" HD in full sized PC's, but you can still get them at good prices these days.

First thing to find out is if your laptop is using SATA or IDE drives. I'm guessing IDE as only the latest are SATA, but it is worth double checking before you buy one. The second is to double check the maximum size of drive your laptop supports. A lot of laptops to still have HD size limitations, but again recent ones should be OK.

As for actual size. As always, get the largest drive you can afford. However laptop drives (due to being 2.5") are still not available in sizes as large as 3.5" desktop drives. A 250GB drive is the largest you will find most of the time, with 320GB being the largest I've seen to date.

A Seagate 160GB 2.5" IDE HD costs about £38
A WD 250GB 2.5" HD costs about £53

If however you find your laptop can use SATA drives then you can get them up to 500GB. But they are still quite expensive at that size.

A Hitachi Travelstar 500GB 2.5" SATA HD is £144, but I would avoid Hitachi drives where possible.

Go for Seagate if you can, and Samsung if not. WD drives are reliable but a bit noisy. Other laptop makes include Fujisu and Toshiba. I've no experience using those, but they should both be good.