I just reformatted the hard drive (Windows XP Pro both before and after), and I get that message to Please select an operating system. The thing is, I don't think I have any partitions (when I reformatted, it looked like there was a second partition with 8 MB on it, but I figured that to be normal. Moreover, the main partition said it was using the max space).
I also tried to boot from the other "operating system," but it gave an error saying that it couldn't. I've read a few posts in various forums saying to either reformat or to mess with the boot.ini file; I don't mind doing the latter, but I want to make sure that there are no other partitions or old chunks of data lying about.