|Belly up on the computer. If the motherboard is defective chances are the power supply caused it. Emachines are notorious for crappy power suplies that burn out. When they do they may take other hardware with them. |
A computer with those specs isn't worth what it will cost to fix.
Besides that, changing the MBoard will most likely prevent Windows from working. The OEM versions of Windows are keyed to the original motherboard.
You can slave the drive to a different computer to recover any data you need.