Windy I think I got my memory from Crucial. They ensured I got the right stick and their website FAQ sorted on a problem of my own making.
It is worth delving in the laptop first to ensure you know what is there already. I just added 1Gb to my 256Mb. Knowing the effect next time I would ditch the 256 and go for 2 x 1Gb. You can't have too much memory (well you can if your computer can't handle it) but it has a dramatic effect on page file usage.