以下範例是從Centos 5 64-bit變更為Centos 5 32-bit

Assuming you currently have a Centos 5 64-bit that was installed by us (if you have or want 32-bit, set/use 32-bit accordingly).
Below will reinstall to Centos 5.6 64-bit, change it accordingly if you want other versions of centos.
1. SSH to your server and login as root
2. Type below:

3. Add to/Edit the grub menu.lst entry to load the pxe kernel (note: if you were already using grub you do not need to type again the first 2 lines)

nano -w /etc/grub.conf

in that file paste this in BETWEEN "hiddenmenu" and "title CentOS..." (IMPORTANT): 
title Centos Install (PXE)
root (hd0,0)
kernel /vmlinuz.cent.pxe vnc vncpassword=YOURPSW headless ip=YOURIP netmask=255.255.255.0 gateway=GATEWAYIP dns=8.8.8.8 ksdevice=eth0 method=http://vault.centos.org/5.6/os/x86_64/ lang=en_US keymap=us
initrd /initrd.img.cent.pxe

replace

YOURPSW with the VNC password you want setup
YOURIP with the ip of the box…
GATEWAYIP with the gateway assigned to your box

Hint: you can see the gateway ip by issuing

route -n | grep UG

once you have done this you need to count the number of times “title” appears in the file, press ctrl +x, and save the file

4. Reboot the server by typing
reboot

5. Assuming above is done correctly, you can then use vncviewer (download from realvnc.com) and connect to YOURIPHERE:1

And password is whatever you set above.