linux any version for compaq celeron 420 @1.6GHz 512 Mb ram

I suggest using Ubuntu. It is very user friendly and easy to use. Plus if you have any questions about Ubuntu you can ask them here.

Yes, apart from the 512Mb ram everything looks well over the min.spec. for Ubuntu :) Try it as a LiveCd first

http://www.ubuntu.com/getubuntu/download

https://help.ubuntu.com/community/LiveCD

Pretty much any desktop version of linux is going to do a good job at this. I would recommend Ubuntu 32bit version because it's so easy to get help for it and also tends to be so easy to use in the first place.

Of course we would say that but other forums good to ask this type of question in are
http://www.linuxquestions.org
http://distrowatch.com/weekly.php?issue=20090831&mode=67#comments
Note the DistroWatch is not really a Answers Forum like this one but is meant to be a discussion and comments about this weeks articles but it often goes a bit sideways from there - just look in previous weeks threads to see how off-topic they get ;) It's good to get them back on track by getting them back to talking about their favourite distros ;)

The best forum is LinuxQuestions for this tyoe of question imo
Good luck and regards from
Tom :)

whole configuration match this ubuntu or i386 having some problem

Hi :)

Usually the best way to find out is to download the iso of a distro such as Ubuntu then make a cd of it
https://help.ubuntu.com/community/BurningIsoHowto
and finally see if you can boot-up your machine with it.

If you are not on unlimited broadband then it might be better to check your machines hardware against the lists of compatible hardware but these lists are often incomplete as people seldom write in to say they haven't got a problem, they tend to stay quiet if everything works.
https://help.ubuntu.com/8.04/switching/preparing-hardware.html
Also as Ubuntu keeps getting updated we find things work that didn't used to but occasionally we lose something although that doesn't happen very often.

So really the best way is to try it and see. If you are on a limited download, such as wireless or something then perhaps try a very tiny and light distro called sliTaz to see if that works. It's only 30Mb so there's a lot it can't do but it is a good one to try out
http://distrowatch.com/table.php?distribution=slitaz

Good luck and regards from
Tom :)