Windows 7 RTM shutdown anomaly

I have an Amilo-Pro 3505 with Windows 7 installed plus an external Samsung HDD on USB. If I issue a shutdown command, the laptop doesn't seem to shut down completely as the fan is still running. I cannot do much (the 5sec power button doesn't do anything), and have to unplug the HDD USB cabel to finally observe a shutdown. If I have the HDD plugged in, my laptop doesn't seem to start at all on power on (fans going, but black screen). (The same external HDD caused no trouble on my Acer Travelmate 2492 with W7)

Why is that? Do I need to set power options around?

Solution 1:

You could try updating the BIOS. BIOS updates can sometimes fix issues such as this. (read the manufacturers warnings before proceeding with this)

Solution 2:

I guess I found the explanation. The USB cord back-powers my computer after the shutdown up to a certain level: the 5V is enough to start the fan and the DVD self-init, but not enough to power the entire machine. This voltage interferes with the regular power supply and can not correctly start or stop the machine. The solution is to turn off or pull out the external rack before I start or stop the laptop.