I know that feeling. I've been there.
"I've lost all my photos/videos/information" is usually the first thought to cross your mind, and it's true. At that point, you have lost your important data, because you can't access the hard drive.
"When did I last do a backup?" is probably the next thing you think. The answer is usually "Months ago" or perhaps even more likely, "Never". That's not good news.
After trying a dozen times to get the system to reboot, there's nothing else you can do, is there?
Well, actually, there might be. Did the system try to load? Did you briefly see the usual images you used to see when it still used to work, you know, the Windows logo, or coloured blobs floating around, or some other indication that Windows is still in there somewhere? If you did see that, there's a reasonable chance you might be able to recover some, or even all, of your lost data - if you're lucky, and even if you didn't, it's still worth a try. At this point you have nothing to lose.
There are a few ways to try to recover your files, but the easiest and cheapest way is to use a Linux 'Live' CD, ideally Puppy Linux, which is better than cheap, it's free. Most Linux distributions are free, in fact, but Puppy is smaller to download and simpler to use than the rest.
The first thing to do is to download a copy of Puppy Linux from here. If your faulty computer is old, I would suggest downloading the 32 bit version, unless you know it has a 64 bit system, or is fairly new, in which case you should probably download the 64 bit version. If one doesn't work, try the other, all it will cost you is another blank CD. The current version name is Slacko, so don't panic when the filename doesn't say Puppy.
When the download is complete, right click on the file, and select 'Burn disk image'. Put a blank CD into the CD drive, and click the 'Burn' button. If you're sensible and methodical, you will at this point label your new CD for future reference, or if you're like me, you will trust your memory, lose the disc, and have to download and burn it again when you next need it. Hopefully, you now have the means to rescue your data.
Put the CD in the CD drive of your faulty computer, and switch on the power. As the system boots, it may appear to stop working from time to time, but be patient, and after a few minutes, you should see a desktop, which should look vaguely similar to a Windows desktop, and there will be a Quick setup box on the desktop.
As this is only a rescue mission, there's not much point setting up the keyboard or clock, so just click the OK button to use the default settings. A welcome screen will appear, but you can just click the button at top right to close that too.
OK, you're ready to see if your data still exists. At bottom left of the desktop, you should see one or more images representing hard drives, labeled sda1, sda2, etc, and another representing a CD drive, labeled sr0. Sda 1 will usually be your Windows system drive, so SINGLE click on that, and the folders and files on the drive will be displayed.
You should then be able to see Documents and Settings, and SINGLE click that to open it. The various windows should all look quite familiar, rather like on Windows, but just a bit 'clunkier'.
If you're lucky, all your documents and photos will be there, safe and sound, at which point you can relax a bit. You could test one or two of the photos by single clicking on their icons, but most Windows documents won't open, because there's no suitable program to open them. Don't worry, if they are there they should be OK.
Now we come to the main part of the rescue mission. Plug in a USB memory stick, and a USB drive icon labeled sdb1 should appear at bottom left of the desktop, so single click on it, and it should open.
In the Documents folder, or wherever your data is, select a group of photos or documents, that will fit onto your USB stick, and holding the left mouse button down, 'drag' them to the USB drive window, and release the mouse button. A box will pop up, with options to Copy, Move or Link. I usually select Copy, in case something goes wrong in the transfer to a working PC, because the documents are still available on the faulty PC for a second attempt. If you Move them, you don't get a second chance.
Once all documents have been copied, or the USB stick is full, close the USB stick window, right click on the USB stick icon on the desktop, and select Unmount sdb1 (if currently mounted). You can then remove the USB stick, and transfer the recovered files to a working PC or laptop. That's it, unless there are more files to recover, in which case you just plug in the USB stick again, and repeat the selecting and copying process.
To exit from Puppy Linux, remove the CD from the CD drive, click the Menu button at bottom left, where the Windows start button usually is, and select Leave. In the Log out box, select Shut Down. You will be given the option to Save, but just select No. All done, and hopefully your documents are now all available again on the other computer.