|Given the time you bought it and it is still running......|
The Bestech power supply used in E-machines has, or seems to have a built in end of life function. When it goes it can take out everything. mb,hd,cdrom,memory,cpu.
If you get your posted problem fixed, look for another power supply and replace it......ten minute job....and then get another few years of service from the computer.
It doesn't have to be an expensive high end PS just not another Bestech.