If the system case is a mini type(or not), being very small then venting the heat build-up is very important. The original system came with 1 HD no though. Once you install the 2nd HD and probably over the other one, it creates a *hot spot* between the two. This in turn creates a stressful situation that over time will kill the HD(s). While no real testing in this area has been noted by me, I find it hard to understand why 1 solo HD works great for a long time and then when a 2nd HD is installed that shorty after(30days or more) issues arise. In such cases, cooling is paramount to system survival. Added cooling is critical and doing so will greatly increase the chance of system uptime. HOWEVER, it doesn't remove the "hot spot" between the 2 HDs that still exists, it just tends to be less stressful as long as proper cooling continues. Added devices or goodies will only add heat to that to include the PSU which in turn it also becomes strained as it is a primary heat exhaust, so a dual fanned PSU is practically a must have. While 500W is enough, a cheap unit claiming 500W is really offering roughly 75% of that on a steady basis once into 80% or more it becomes unstable, thus cheap is cheap. Understand also, that mini system case tend to have int. airflow issues and provides little in a way of cooler air as the space itself is limited to circulate air. Here the air flow pattern is disrupted into a confusing pattern which may not benefit at levels wanted, so again I stress better cooling whenever possible.
I recently purchased an Asus T-Series barebones pc.
http://reviews.cnet.com/barebones-pcs/asus-t-series-t3/4505-11485_7-32171954.html (not the exact model)
I ended up putting a 7950 Nvidia graphics card and a 500w psu inside, alongwith two hard drives.
Both hd's have since died on me within the space of 4 months. I'm trying to figure out if this was just bad luck or something to do with overheating hd's? Their mount is directly above the cpu fan.
Intel Core 2 Duo E7500 LGA775 'Wolfdale' 2.93GHz (1066FSB)
Corsair XMS2 4GB (2x2GB) DDR2 PC2-6400C5 TwinX Dual Channel (TWIN2X4096-6400C5)
hd1: 160GB Western Digital
hd2: 1TB SAMSUNG
Have been using both Win7 and XP