The best thing to do at such a time is a System Restore, which rolls back your system (your computer) to a state where it worked.
Unfortunately, Microsoft, in its wisdom, gives you a very complicated set of instructions on how to do this (if you actually do know how to use the "Help" feature, which will take an entire textbook to explain).
The irony is, Microsoft has actually coded a very simple way to do a System Restore. It's easy to use and easy to remember. Here's how to do it:
- Restart your computer
- When you see the memory check at the top left of your screen, repeatedly hit the F8 function key at the top of your keyboard (it's above and between the 9 and 0 keys at the top).
- You'll be presented with a text-only screen that has various options. Use the Up/Down arrow keys of your keyboard to highlight "Last Known Good Configuration" and hit enter.
- For some odd reason, you'll be asked which Operating System to use. Since most people use Windows XP, that'll be the only option shown and highlighted. Hit enter. If you're one of those experimentative (I made that word up) types who has more than one OS (Operating System) installed and Windows XP isn't the one highlighted, highlight it with the arrow keys and then hit enter
There's a drawback to System Restore, of course. Any programs or software you install between the last known good configuration and the time the computer stopped working will disappear. Since it was probably one of those programs that caused the problem this is a good thing. If you think you absolutely MUST have those programs/software install them one at a time and reboot between each installation. If your computer behaves oddly after reboot do a System Restore and ditch the last piece of software installed (if you bought it, go back to the seller for a refund).