There are several errors that can occur during the boot process or Windows startup.
If there are errors during the POST, the system might display a numeric error message. Typically, you can press F1 to acknowledge the error and continue booting.
For other POST errors, a series of audible beeps will tell you if a problem has been detected. The sequence of beeps is a code that indicates the type of problem.
Invalid boot disk
The most common cause of this is a non-bootable disk in a drive. If your system has ﬂoppy-disk drives, or bootable CD-ROM or thumb drives, check to see if you need to remove a disk from the drive. However, there could be a hardware problem with the hard disk. Also verify that CMOS is set to boot from the hard drive. Most BIOSes allow for the conﬁguration of four or more boot devices as ﬁrst, second, third, etc. If one fails, it will automatically try the next in line. The only way this process will fail is if the boot devices are set to None or all the same (which many do not allow). Also, it cannot be assumed that the user will want the CMOS to be set to “boot from the hard drive,” since many times there is a need to boot from CD, or even boot through the network.
Inaccessible boot device
There might be a hardware problem with the hard disk or hard disk controller. Check hard drive and hard drive controller connections.
In Windows XP, the NTLDR ﬁle might be missing or corrupt, in which case you might need to copy it from the Windows CD-ROM. However, the most common problem is that there is a non-bootable disk in the drive.
Other missing Windows startup ﬁles
If Ntoskrnl is missing, you can copy it from the Windows installation CD-ROM. This error can also indicate a problem in the ARC path speciﬁcations in the Boot.ini ﬁle.
If Bootsect.dos is missing on a dual-boot system, you will have to restore it from a backup ﬁle, as its contents are speciﬁc to a particular system. System ﬁles should not be deleted or become corrupt during normal system operation, so these errors are rare. They might indicate an underlying hardware problem, a disk error, or the presence of a computer virus.
Device or service failed during startup
There might be a problem with a missing or corrupted device driver, or there could be hardware resource conﬂicts (although this is rare on a Plug and Play [PnP] system).
Device or program in Registry not found
A device driver or related ﬁle might be missing or damaged. You might need to reinstall the device.
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