I am not sure is this is the place to discuss this, but I'll give it a go.
I am currently running windows 7 (x64)on a laptop with 1GB of ram. And it runs really slow (like the 'I need to wait for the characters to show up when typing' kind of slow).
Ok, this x64 part was a mistake of course. I liked the idea to be able to run programs, even when there would be only a x64 edition of it.
I tried running window xp on it before and it works really well driverwise, however what kept me from downgrading until now is the following.
While in windows 7 there is an option to adjust the screen brightness in the power options and my screen can be really bright when I do not use this. I don't think my back-light is dimmable (or is it? I am talking about a Sony Vaio VPCW21S1E), the function probbably just adust the pixel 'transparency'.
I tried different programs under windows xp to change the screen brightness but most of them behaved really buggy. Any suggestions?