These are the symptoms of a heat and/or power issue, usually associated with the GPU and/or PSU.
What are the specs for this system and are you overclocking anything (CPU, GPU, memory)?
BTW, what HDD fan are you referring to? Do you mean front case fan?
MOBO: ASUS P8Z77 V - Pro
CPU: Intel Core i5 2500k
GPU: GIGABYTE Nvidia GTX 660 ti OC
RAM: Kingston 16GB (2x8)
Sound Card: ASUS Xonar D1
PSU: Corsair TX 650 Enthusiast Series
Speakers: Edifier DA5000 Pro 5.1
HDD: Seagate Barracuda 500GB + Seagate Barracuda 2TB
only thing OC'ed is the GPU which is the overclocked version, I didn't change anything at all.
By HDD fan I'm refering to the front case fan, yes, it's not working and I was thinking maybe the HDDs had a hard time crossing the desert.
The thing is I get black screen (monitor displays no signal and "resets" to desktop afterwards) with games I used to play with my 5-year-old gpu I recently replaced.
all drivers are up-to-date, so, what else could be the case?