I was formatting my external hard drive (LaCie 500GB) on my iMac using the disc utility and it didn't complete. Now the device wont appear anywhere.

I tried it on my PC
(windows 7) and it appeared under 'disk management' and I tried to initialize it (which I believe is the right thing to do?) it error-ed saying "device is not ready" or something similar.

It now has disappeared from there and I can only see it under 'device manager' and even now it jumps from being under 'disk drives' to 'universal serial bus controllers'.

It is making a different noise to how it always used to but it doesn't sound sick... could this be because its empty and searching or something? It is also a lot hotter than usual.. if that means anything?

As you can probably tell, I don't really know what I'm doing. Is it possible to save it or have I stuffed it up? If it is ruined.. any suggestions on what brand is good to buy a new one?
NEED HELP!
THANKYOU!!!!!!!!!

If you formatted on a Mac, you most likely formated with HFS+. Without drivers that cost about 40 dollars or more, you can't view HFS+ drives in Windows.

Format the drive again on your iMac, but when you format, there should be an option that says FAT instead of HFS+ under the Erase tab. Make sure you select FAT instead.

Now this is a huge dilemma. Windows can't read or write HFS+, but it can read/write NTFS and FAT. OS X can read/write FAT, but it can only read NTFS (costly drivers and potentially drive-corrupting hacks aside). You probably will say "Well can't I just use FAT?" Turns out that FAT has one huge limitation: you can't store files bigger than 4GB. This may not matter to you, but it doesn't work for me since I have several blu ray rips that are upwards of 10GB. So this may not matter to you, in which case you should use FAT, but otherwise you have a dilemma. I recommend buying an NTFS driver from Paragon for NTFS so you can make your mac NTFS compatible (read/write).

try some disk recovery tools..

if its making sounds, try to plug to another usb port, or your friend PC or laptop...

You said you formatted it on your iMac, that might be your issue.
Mac uses a specific file system format (much as windows uses NTFS).
Try to reformat it using FAT32, it might just say FAT; Just don't use ExtFAT because thats windows only more or less.

FAT32 is the default that most external drives come formatted with because it is recognizable in all (or nearly all) operating systems (Linux, Unix, Mac, Windows, Etc). Its only downside is that the individual file size is limited, but thats rarely a problem unless your placing DVD ISOs on it.

If it doesn't show up on your windows machine, attempt to look at it on your mac because windows might be unable to figure out what its trying to look at after what happened on the mac. If that doesn't work either then check with the manufacturer for a boot utility (a cd that you burn with programs for formatting/repairing the hard drive). If there isn't one you can try the UBCD (Ultimate Boot CD) as it has a great number of utilities on it. You could also try linux (Ubuntu has a LiveCD option so that you can run it off a CD and then attempt to access your disk).

EDIT - Side note, you said it's making noise. I don't know what kind of external drive you have but if its a laptop drive (tiny, no external power supply) then it could be it isn't getting enough power, try a different usb port (some of them are limited in the amount of power they can give off) or see if you have a cable that came with it with multiple plugs on the computer side - these are so that it can draw power from more then one usb port. Its usually got one usb jack on the drive's side and then 2 on the computer's side.
Hope that helps