A lot of speed difference when you upgrade from 256-512. However, I don't notice too much improvement when I upgrade my 512 to 1gig. Maybe because I'm not a gamer and don't use too complicated stuff with my notebook.
I am trying to run Windows XP SP 2 on my Dell Inspiron 1100, and it only has 256 MB (2x12
of PC2100 memory. I just bought two 256 MB sticks to boost me up to 512.
How much of an overall performance should I feel? If any.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic