Trust me the Green drives are no good as boot drives but continue using it if you want to. The choice is yours.
That may not be the cause of your trouble though if as you said the problem was there befopre you changed drives. It could be a faulty/dirty mainds supply. It only needs to drop a bit or fail for a millisecond to reset the computer. Hav you got access to a UPS system you could try ?
The causes related to power surges, or unstable power supply was my second suspect (after the hard drive) and I tried two different power supplies (one from a 600W other 400W), both made in reasonable quality. I did not notice any improvement. My main supply is well done and I never had defects in the past. I also believe that sudden drops in voltage, or power problems, would lead to an immediate shutdown of the PC, made by motherboard to protect himself. Instead,the image remains frozen for 5-8 seconds which makes me think of a communication error between some component and the motherboard.
I noticed that the problem always occurs when the CPU load is low, and the disk is in read / write, even if for example you are playing a movie at 1080p on the external USB drive. even, when you copy files in the main drive. Never when the OS is loading.
It could not be a problem with flows between motherboard and SATA / USB? There is a method to test this switch?
off topic: I used a green driver just thinking of a typical use for HTPC, low performance, but with plate that run more slowly, less consumption, and lower load energy. Why not green hard drivers are not suitable for boot? I searched in the internet, but have not found any information to support this theory...