If the message about the reasons for the stop loading your BIOS does not display with the message about pressing F1, then press that key and read the informational message - the further actions depend on the contents of the inscription. Perhaps it will not work once, because sometimes the system gives very little time to review the information and these lines are replaced by information about the subsequent procedures of the boot process. In this case, try to restart the computer several times, or perhaps take a picture of the screen on a mobile phone.
One of the most frequent reasons for the stop loading is no floppy disk in the drive, it informs the message system. In the settings panel there is a BIOS setting that sets the order of the survey drives in search of the operating system loader. If the first in this list is the floppy drive, and its just physically not present in your computer, then it becomes the reason for stopping the download procedure. To eliminate this cause easily by changing the order of survey in the BIOS settings or even disabling the polling of the floppy drive.
Another reason could be too low rotation speed CPU fan (cooler). This reason is eliminated either by a change of the rotational speed of the cooler, or threshold, in the BIOS settings. In addition, there is a probability of failure of the speed sensor. This is a rather dangerous fault, which is potentially threatened by a failure of the processor.
Sometimes changes in BIOS that you do to eliminate the reasons for the stop loading the OS, every time reset and the problem recurs. In this case, replace the rechargeable battery on the motherboard of the computer.
If the cause is identified, it is not dangerous, but to fix it you can't, you can temporarily disable in the BIOS setting that makes it stop loading. In different versions this is done a little differently, but you should start with a search on the MAIN tab, the option called HALT ON - he needs to set the value for NO ERROR and save the changes.