Looking for answers.

[msrhonda]

I have an Emachines computer, OS is Windows 7. I turned on the computer one day and there is a black screen stating Boot from CD: NVIDIA Boot Agent 249.0542.
PXE-E53 No Boot file received.
PXE-MOF: Exiting NVIDIA Boot Agent
Disk Boot Failure Insert system disk and press enter.

I don't have a system disk, I don't think I ever had one for this computer.
Can't access windows at all, but I can press Delete and access the BIOS CMOS Setup Utility:
it has the time and date, Sata 1 [None]
SATA 2 [ATAPI DVD A DH16A]
Halt On [All , But Keyboard ]
DIMM1 1024MB
DIMM2 1024MB
Total Memory 2048MB

 

[Paul NZ]

Make sure the hdd is the bootdisk. And check the sata cables

 

[4745454b]

Looks like your harddrive (HDD) isn't being seen anymore. If the SATA ports start at 2, and it's the DVD drive then it isn't seeing the HDD on SATA 1. If it's an older machine that is out of warranty then you can open it and see if any cords are removed/hanging. But you have an issue with your HDD.