This is an old machine on which I had Fedora 6 perfectly running. So I updated the BIOS to its latest version (A13) and attempted to install 6.2. The CD is fine since I verified it and also used it to install in another system. It starts fine but it gets stuck when printing the following line:

starting NFS statd:

I played a bit with different BIOS settings but nothing worked. So I attempted with both a Fedora 15 and a Ubuntu 11.10 installations and in both cases freeze. In the Ubuntu case, I tried all possible boot options in the menu, but none worked. So finally I took a Windows XP installation CD and went through without a hitch. Once XP was installed I tried with the WUBI installation program that installs from within XP but also it got stuck. I definitively would like to have Centos running on this machine, there is any hope?

Sounds rather doubtful after all those failures. Are all related to networking? You might try the LiveCD/DVD as a test/diagnostic tool.

Again, the system gets stuck with the Live CD, so I cannot do anything. Today, while in the information given by the BIOS page, I saw that the memory is 1GB, distributed in 4 rambus sticks. Two of them are non-ECC and two are ECC. Would that be cause for the live CD to get stuck? It didn't with windows XP nor when I installed FC6 in the past.

A Linux kernel is rather particular about its system RAM. The golden rule is to ensure that the RAM matches is type, speed and size.

You could try removing two of the banks and then see if the "live CD to get stuck". (Whatever that means.) Is there any chance you could borrow a matching set of RAM banks, just to test the hardware, thus deciding if attempts to use that hardware is a "lost cause"?

I swap the non-ECC sticks for ECC but it didn't make any difference. It still freezes without any particular message after OK'ing all steps. What is puzzling to me is why Windows XP installs without any problem and none of the Linux distros don't.

Possibly because Linux uses system resources differently than Windows. Please try running memtest86+ from the LiveCD at least overnight - 24 hours or more is better - and see if you get any errors.