Which version of centos should i install?
 

Sorry totally clueless here the manufacturer of my server installed centos 5.4 on my server about 1 year ago but I have had my server in storage for the last year and I want to do a clean install on it.

Which version of centos should i install i386 or x86_64 my server has 8 Intel(R) Xeon(R) cpu E5405 @2.00GHZ in it.

Google shows that your CPU has 64-bit capabilities so you could install x86_64.
If you still can, check 'uname -a' to see which architecture the manufacturer put on the machine
btw, how much RAM have you got on it?

uname result
 

hi uname-a returned this RAM can't remember how do i check that?

[root@localhost ~]# uname -a
Linux localhost.localdomain 2.6.18-128.1.16.el5xen #1 SMP Tue Jun 30 07:20:15 EDT 2009 i686 i686 i386 GNU/Linux
[root@localhost ~]#

or

[root@localhost ~]# dmesg | grep ^Memory:
Memory: 3635224k/3757428k available (2128k kernel code, 112740k reserved, 877k data, 176k init, 3011964k highmem)

not sure which is what

It looks like you have 4GB of RAM (not all of which is utilised due to architecture limitations)
You might install x86_64 to utilise slightly more RAM. I don't think, however, that the difference will be visible.
Do you know the exact model of the whole computer? Was it custom built or bought from a store?

It was custom built by a company in Thailand who are certified intel server builders.

The server housing actually has an intel logo Intel Xeon Siligon

If you've got 4GB, it doesn't make MUCH difference which architecture you go for. You could, however, doublecheck the amount of memory when you boot the computer (in BIOS) to make sure you don't have more than 4GB RAM in which case you'd be better off using x86_64. I doubt it, though - in that case the manufacturer wouldn't have preinstalled CentOS i386.

On reboot it says I have 4GB so I should go with the centos 5.5 64 bit installation?

Do i need to format my sytem first?

Yes, you can go for 64-bit.
You don't need to format your partitions beforehand. Download a CentOS image, burn it on a DVD and boot the machine off the DVD.
During the installation process you'll be asked to partition (and format) the hard drive.
BTW, PLEASE BACKUP ANY IMPORTANT DATA BEFORE YOU START.
Here's some info on partitioning centos

thank you very much for all the help I shall try to start now. I don't believe I have any important info saved on the server as I have never used it before.