Other, more knowledgeable people will be along shortly, but just to let you know that I did the same thing some years ago.
Firstly, do not switch on the affected machine, as this could overwrite files on your disk that you want to recover. Its probably preferable to remove the disk and put it in to another machine, either inside the case as a slave or in a hard disk caddy connected by usb. Ensure you dont boot from the affected disk!
Get some disk recovery software (I got restorer 2000) and then run it on the affected disk. It will recover as many files as it can, and you can then copy them somewhere safe.
Doing this I managed to recover the vast majority of my files. Your chances of success are greater, the larger original size of the disk, as the operating system has less of a chance to overwrite your old files.
With restorer 2000, you can run a free version, which will allow you to recover small files, just to see that it works. (It will show you all the filenames that it finds, just that only the paid for version will recover the larger sizes. I did have some 200Mb video files which wouldn't open though, presumably because some small part was correuptred.)
Best of luck - and whilst your're waiting for otehr answers to come along, work out your new backup procedures so you're not stuck like this again!
Last edited by curmudgeon; 14th April 2007 at 11:53.
Reason: cross posted with Cypherus nice to see we're both saying roughly the same thing!