There are some events where your system may be putting in its resignation letter because it is "overwhelmed" to some extent
But in some cases these things can be resolved by applying some advanced technology remedies.
Some possible causes that may make this necessary are:
Newer systems have been known to get weighed down by newly developed applications or early production mistakes.
They also may have driver errors or may become error prone when using software that was upgraded.
If your computer has some sort of component that is failing to properly work, it can make it to where the system cannot boot because it can't handle certain information it needs to successfully continue.
In some rare cases, software error or a system crash during an update process (something similar) can happen and cause your system to lose it's boot configuration and operating system information.
The 1st common cause: Virus
A computer virus is a surefire way to make sure that your computer doesn't last very long. If you know or even suspect that a virus is present on your computer, you should have a professional examine it immediately to prevent damage that could make your system unusable.
Other Cause: SpyWare
Secret access to your private life and extremely secure information is not something to take lightly. If you have spyware on your system, you could easily be setting yourself up for something much much worse.
Spyware applications can put a tremendous amount of strain on the physical aspects of your system as well, which in the end can cause it to crash and fail.