There are a few reasons this might happen.
- Third-party software, probably AV, can deactivate or corrupt your Master Boot Record (probably the case).
- The boot settings in your BIOS were changed.
Make sure your boot settings are correct and use a windows boot disc, or partition if you have a newer notebook (Read any manuals that came with it). And use the system restore setting and revert back to a previously saved restore point.
If the drive suffered a physical crash, you would definitely hear noises coming from it and would probably never get past the "No Fixed Disk Present. Insert System Disk and Press Enter" error. If you do get this error even after checking if your boot settings are correct and all connections are seated properly in the disk, or hear noises... DO NOT run stuff like chdisk or any diagnostic software. Because any further writing/re-writing could cause permanent data loss.
If the above didn't render any results, try using software like Norton Ghost or mount the drive in an external HDD case and backup data using a healthy machine. Run the backed up data through an anti-virus just to make sure. Once everything is backed up, then you can run diagnostic software on the hard drive to see if it can still be used.
If all else fails--bricked hard drives make great targets.