Loud fan running all the time sounds like a jet taking off.

with that info I can only assume you need a new fan motor.

usually that sound is associated with a defective clutch fan... did you get the right one for your application... thermal or non thermal

did you purchase an after market cheap one... I'd replace it with another one and try again

there are 3 speeds for that fan sounds like its at the highest speed might be a relay problem or a temp sensor problem. and that fan isn't 800.00 dollars someone is kidding you call a parts place yourself. although there should be no reason to replace it this time

your fan may be running all the time, or possibly a vacuum leak but if it were one loud enough to hear you car would be running rough.

unplug the not working fan and jumper 12 volts to it. if it works then wiring or sensor is bad

THIS IS NORMAL!!!
When the machine boots up the fans are running at full speed, and after a moment the bios loads teh power management that lowers the fans to the needed speeds. If you tax your computer the fans will speed up to compensate for the heat produced and will get louder then as well...
The larger and more powerful your CPU and Video Card the louder the startup will be. Some of the newest quad core computers with high dollar vido cards will sound like a jet taking off when starting up, I know mine does!

Not sure how long you have had the Desktop. However it will be one of two things. If it used to run quitely and now is making lots of noise then immediately take it to be replaced. Fans on power supplies cannot be fixed. If it should stop completely then the heat that builds up in your desktop could damage your components. Second, if it is fairly new and has always sounded that way then you are ok. Yes, there are some fans that are very loud, again you can have it replaced. They sell "quite fans" now that make no noise at all. But first and foremost if you start having problems like unusual reboots, lock ups, etc then your computer is getting overheated and the power supply which houses the fan needs to be replaced. Hope this helps.

take raer panel off inside freezer and check there is no ice build up which is hitting the fan

In side you're ZV5000 are two fans. These fans sit on a spindle which spins. The spindle may be worn which is giving you that loud noise. (Or a fan blade could be bent or warped from heat).
The fan it’s self may be loose & can be tightened.
The only way to check if the spindle is worn would be to dissemble the ZV5000. With the correct instruction you can check the fans. (And also clean the fans & copper heat sinks).
Here is a link to do this you're self, including pictures.
http://www.instructables.com/id/Cleaning-Your-Laptop-Cooling-System/
It's worth taking a look & saving you're self a few bucks.

Good Luck & take you time!
Mike

Dont worry Rob5150, this is normal in hp laptops, this should not be bothering u any more. But there are modes in which u can make the fan run either always ON or when required.

Thankyou