Bad luck or what...?

[Lorand]

A friend of mine had five hard-disk crashes in a row... All HDDs were brand new (different models). The crashes weren’t physical, the HDD electronic circuit got fried. The last one lasted only one day...
What could be wrong with his computer?
The PSU? The motherboard? Then why the cd-roms survive?

 

[Praetor]

1. My first guess is PSU
2. Dont think the mobo is to blame unless you can actually see popped capacitors or something
3. CDROMs (a) wont fry if they arent "active", (b) are designed to take a lot more punishment (voltage wise) than HDDs.

 

[Lorand]

Why are hard disks so sensitive? Once I accidentally shortcircuited a motherboard's USB pinout (I didn't read what are exactly the pin assignments ) and nothing happened. The computer did shut itself down, but nothing get fried... After reading the pin assignments I realized that the 5 V went straight into the mobo ground...

 

[Praetor]

Why are hard disks so sensitive?

They're not "sooooooo" sensitive. It's just that optical drives are designed with variable power in mind hence they can handle a wider range of voltages.