I just purchased a new Seagate 1.5TB hard drive from newegg.com. I read a lot of mixed reviews of them being DOA, and some failing within days.

I installed it in my system Wednesday night and loaded a new copy of Vista Home Premium.

I noticed that randomly something (I'm thinking the new drive, but could be the old one) sounds like it shuts down, and then starts right back up. I'm sure you all know what a shutting down hard drive sounds like.

My OS never freezes when this happens. My old drive worked perfectly so I am not convinced this is the problem. Is this a common issue? A drive powering down and back up on it's own? Is it a sign of an under powered power supply? I don't understand how the OS doesn't freeze.

Any suggestions

If the OS isn't actively performing reads or writes on the drive at the time it'll continue on just fine from what it already has in RAM. It does sound like what I wound up with on an old power supply I had that I put too much load on... my solution at the time was a bit unorthodox (and required being very careful). I powered my hard drives and cdrom from a different computer/power supply. Just remembering to always make sure the drives are powered up first and down last was more gray hair than I needed.

Check your System Event Log (Right Click My Computer -> System Tools -> Event Viewer -> System). If it's a hard drive acting like it's failing there will be a good few messages from the source "disk". If the drive's not getting enough power to stay up it'll still act like it's failing, but knowing (with certainty) that it is the drive making the sound, and which drive (details on the errors will let you track down which disk) will narrow things down a lot.

First thing I would check is power options to make sure the drive is set to always on or at least 10 min.

'It makes the noise while I am sitting there using it. I've not heard it while it's idle yet, but then again I don't sit in front of it unless I'm using it.

So, to you all it doesn't sound like a bad drive?

you say you have two drives in your computer the first one being the spanky new seagate and the second one the old drive
as augie said check the windows power options i'd say its set to power down a drive after a certain time limit if your not accessing the second drive very often i'd tend to assume that windows is powering it down to save energy it shouldn't be a problem but if your finding the noise disconcerting then set your power options to never turn off the drive this should stop it from makeing the slight click at power down

Sounds normal to me. I know my external hard drive does that when I'm not using it. It spins down and then I hear a click.