I've got a Compaq D500 SFF and have upgraded the hard drive to a larger 400gb. I know this is working ok because I previously used it as an external drive.

I went into the BIOS and confirmed that the hard drive was recognised, then changed to boot firstly off the cd rom and inserted my newly purchased Microsoft Windows XP Prefessional disk.
On re-booting I'm getting error message "Non-System disk or disk error, please strike any key"

I then tried to re-boot from an external cd drive in case the internal cd drive was faulty but same error message.

I purchased this new xp disk from a retailer that stated it could be used on any make of pc, trouble is I have just looked at the cd and it states on the disk "operating system already installed on your computer, reinstallation cd"
This sounds to me that it can only run if the pc is up and running to start with, am I right??
I guess what I am after is a bootable full xp install on a disk.

Please I do hope you have some good news on how to get this sorted.
Sorry for the long post.

Is it a genuine MS XP disk? If yes, then it sounds to me that your bios isn't booting from the CD-drive.

Is there another option to select the boot order without entering bios setup?