Hello, I recently had cause to reinstall Windows XP (I'm old skool). I had the perplexing message "Error Loading Operating System" when it came to the checking hardware stage (at the beginning). When the system restarted I got the previously mentioned message. I did a lot of head scratching and trying different combinations of hardware (HDD + DVD drive) and finally stumbled upon a solution (well it worked for me). When I came to the step which says something like "Where do you want to install the OS" I chose the existing partition that already apparently had an OS installed and chose to reformat the using FAT 32 instead of the usual NTFS option and voila, it all worked perfectly this time. Not enough of an expert to know what's going on here, but try selecting FAT 32 and formatting the drive and see how you get on.