Whether caused by a virus, a new operating system or by simple mistake, being faced with an “Operating System not found” or similar error during your computer system’s boot up can be a nerve rattling experience
By Perseverance Tavagwisa
First, check your BIOS and hardware
In many cases, having Windows 7 fail to boot may be as simple as having your BIOS set with an incorrect boot order sequence. It can be quite common if you have more than one hard drive installed in your computer and your BIOS gets reset. Usually you can access your BIOS seconds after your computer turns on by pressing the Delete button or by pressing a specific function key. Once in the BIOS, check to see that your system drive is listed appropriately in the boot order sequence; you may need to refer to your motherboard manual for help.
Another possible reason for Windows not being detected upon start up is a hardware issue. If your BIOS is unable to detect your system drive, check to make sure all the cables are plugged in properly. If your hard drive is making an odd noise, such as a clicking sound, your hard drive may be broken. Finally, it is possible that the hard drive is having Data corruption issues, which has damaged important system data, such as the Master Boot Record (MBR). If you suspect a faulty hard drive, it may be a good idea to backup and scan your hard drive for errors from another computer and possibly consider buying a replacement. Trying to repair a boot problem on a damaged drive can possibly lead to even more data loss, so backup your data before attempting anything.
The MBR and other important boot data can also be damaged by trying to install an earlier version of Windows, such as Windows XP (now dysfunctional), alongside Windows 7 and by third-party programs, such as viruses. In the case of a virus, it is recommended that you run a virus scan of the drive before attempting any repairs as otherwise it could lead to more data loss. It is further possible to achieve the appearance of damaged boot data by having the wrong drive partition set to active, which can be the outcome of an overly curious Windows user with administrative permissions.
Fixing the MBR and other start up problems in Windows 7 is most quickly accomplished by using the Windows 7 Installation DVD. If you do not have a Windows 7 Installation DVD however, you can alternatively use a Recovery Disc, which we will show you how to create further down in this article. If you do not yet have either a Windows 7 Installation DVD or a recovery disc, do yourself a big favor and make a recovery disc right away to avoid any unnecessary headaches down the road.