|You may have the boot order set wrong in the BIOS (setup) screens. Check to verify the CD drive is listed BEFORE the hard drive.|
While you are in the setup I suggest you also disable fast boot and any logos so the full POST routine shows at startup. That is the only sure way to know if the BIOS is actually configuring the drives.
I think that with laptop drives it is possible the BIOS may not properly configure a replacement drive and WinXP can. Could even require a BIOS update.
A assume you verified the replacement drive is fully compatible with your laptop?
If it is installed in a removable bay I suggest you re-seat it.