ian phillips, this sounds like you are having trouble with the computer finding the operating system. This could be caused by an hard drive error as well as many other things. I'd go ahead and would try this first. Important If you have not previously set a restore point in System Restore, you cannot restore your computer to a previous state. If you are not sure, or if you have not previously set a restore point, contact Support.
Restore to a point where you know your computer functioned without problems.
To start System Restore using the Command prompt, follow these steps:
Restart your computer, and then press and hold F8 during the initial startup to start your computer in safe mode with a Command prompt.
Use the arrow keys to select the Safe mode with a Command prompt option.
If you are prompted to select an operating system, use the arrow keys to select the appropriate operating system for your computer, and then press ENTER.
Log on as an administrator or with an account that has administrator credentials.
At the command prompt, type %systemroot%\system32\restore\rstrui.exe, and then press ENTER.
Follow the instructions that appear on the screen to restore your computer to a functional state.
you can also try access your BIOS to see if your hard drive still shows up in there. To get to the BIOS
1. Starting with the computer fully off, turn it on by pressing and releasing the power button. Immediately and repeatedly tap the F2 key.
2. The BIOS setup program should appear. If Windows starts, shut down the computer and try step 1 again.
Let us know what you get. Hope this helps, good luck.
Let us know if this makes a difference.