I am using a rather under-powered laptop. Celeron with 512 MB of RAM is not a great configuration have!

Is there any Linux distro that is

1. lightweight

2. has good GUI and

3. supports Laptop hardware like wi-fi, card reader, touchpad etc.

I hope I am not asking for too much!

I guess you would have to specify what you mean by "good GUI". That is rather subjective, as what I would consider good may not be the same as yourself, and vice versa.

As for the others, light distributions will be ones that don't rely on hand-holding and redundant services and tools to keep running. Slackware and Debian are very good bases, as is Gentoo if you want to get a little deeper into it.

In regards to hardware support, all of the distributions use the same kernel (more or less) so they all support the same hardware. Some distributions chose to support more or less hardware out of the box, but there is no hardware that is supported in one distribution but couldn't be supported in any other if you install whatever driver it is using.

Doesn't sound too underpowered to me, depending on which Celeron you have, this is a Celeron M 1.6ghz with 512mb of RAM, runs anything I throw at it. I use Xfce on my preferred distro Arch and it flies, it ran Gnome nicely too, but I prefer Xfce.

You should check out Zenwalk. I'm running it on a laptop, very close to your specs, and it runs great.

www.zenwalk.org

when did 512 mb of ram get to be low specs?, I can just about run anything on my p III with 256 mb of ram

I have found Vector Linux 9 has very good support for hardware. With xfce desktop it is lightweight too! 512mb RAM is suffice for smooth run.