Issue : You are trying to install xenserver 5.6 on an IBM 3850 X5 but the system does not boot / reconise the xenserver 5.6 CD/DVD. If you use the same xenserver 5.6 CD/DVD on another machine it works.

Resolution : This issue had me confused for days? But here is how to get around it.

1. Download the Xenserver 5.6 ISO file from the citrix website.
2. Download the UniNetBootin application from here
3. Insert a USB stick on to your computer
4. Run the program, Select Disk Image > ISO, browse to the xenserver 5.6 ISO you’ve just downloaded, then at the bottom select your USB drive and click on OK. This will now create a bootable USB drive
5. Now put the USB in to your IBM 3850 X5 and turn the server on. If the server does not boot to the USB you might need to go in to the BIOS and change the boot order.