OK, freeze, don't use that computer any more. i don't want to get your hopes up too much.
i had a similar issue when i formatted a hard drive with a lot of data on it.
the less you add to the drive the more chance you have of recovering your data.
you are going to need a piece of software from a company such as on track (google it)
they do a free download to try their software.
it gives a 25 file per session shot, but this will tell you if it is possible to retrieve your files before forking out for the full version.
Not using the computer that you need to recover, download the file. boot your system with the (i think it makes a floppy disc or cd rom). this will then do a search of your harddrive and list all the files it finds. This can take a very long time as your hdd is a large one.
to recover any of your files you are going to need a similar sized or larger hard drive to move the data that you need to. (if it finds what you are looking for.)
if that works, then there are sources on the net that you will be able to glean the full professional product from. but, try the free way first.
see how that goes.