It looks like you have a few viable options to work with. I think it would help to prioritize them for you.1.
Check the CD (or DVD) drive to make sure no disc is still in there. (This is most likely not the problem, seeing as your error message says there is no disk instead of a non-system disk, but this is the easiest first option to try.)2.
Boot up into your BIOS. How you do this will depend on your computer model, but it is most likely done by pressing the F8, Delete or F2 key prior to Windows loading up. You would see a message on your screen after your computer turns on that will indicate which key it is. After you're in the BIOS use the right arrow key to move over to Boot options, then scroll down to the Boot Priority option (or whatever wording seems to point to that option. You will want to make sure that your hard drive is the first boot option. Depending on your machine the way to do that differs, so just look for the on-screen instructions to do it. Make sure to press the proper key (F10 most likely) to save changes and exit. Your computer should reboot into Windows if this was the problem. If not...3.
Open up your PC and make sure that the cable connecting your HD to your PC is plugged in snugly at both ends. If it is already, then replacing the connector cables is an option.
If none of this works, then we'll try other options.
Edited by Eric RBA, 13 August 2009 - 01:42 PM.