Check for the presence of a disk, CD-ROM or DVD-ROM in the reader and remove it if there is one, then restart the PC.
2. The BIOS boot sequence is incorrect
Enter the BIOS setup and modify the boot sequence so that the PC starts first from disk C:
3. Installation of a new hard disk
If it is a newly installed hard disk, it is normal for this message to appear. To solve the problem you only have to insert the system installation CD (usually Windows), then reboot and make sure that the CD-ROM drive is the first one in the boot sequence defined in the BIOS setup.
4. The hard disk is offline
Open the Central Processing Unit (CPU) and verify that the power to the hard disk is connected and the flat cable is well pressed, on the side of the disk and on the side of the motherboard.
5. Corrupt system files
System files that may be necessary for the startup of the PC may have been removed or are corrupted or the disk boot sector is corrupted. To find out, start the PC with a system diskette or the Windows installation CD-ROM (via the Recovery Console) and when you have started, type "Dir C:" to see if you can access the contents of the disk C :. If it is possible, then it is simply a problem of files, now you only have to execute the command:
fdisk /mbr sys c:
Important: Before restoring the boot sector using the fdisk / mbr command, it is recommended, if there is a suspicion of viruses, to use an anti-virus under DOS as f-prot.
The hard disk might be corrupted or the partition might be damaged: if the hard disk was not detected in the BIOS setup. If it is detected, try reinstalling the system with the installation CD, reformatting it, or recovering the partition using a utility.