I have an older generation Intel P III, with a Intel SE440BX-2 (discontinued) mother board and have a small Western Digital Caviar 6GB hard drive with Windows XP Pro installed. Everything works great on this machine. I am trying to upgrade my hard drive with a larger (40GB) - Seagate Barrucuda 7200 drive but when I switch the hard drives and boot up (with Windows XP Pro disk in DVD-ROM drive) I get "Can not find Operating System" on the screen. Does anyone know what might be causing this? If you need more information about other hardware, software, etc., just ask me and I'll be glad to supply it. Help!

Just to clarify: you replaced the 6GB with the 40GB & are now trying to install your full version XP CD? Is this correct?

Is your CD Drive set in the BIOS to boot before the hard drive?