You need to give up on the idea of getting 99% of the data back because most of it is already gone. There are tools that can help in this situation though. I've only done this a few times because it is usually not worth the effort but you may be able to get some of the data back using one of the MANY undelete tools out there. Here is a list of some of them: http://lifehacker.com/5237503/five-best-free-data-recovery-tools This is going to be a long and possibly fruitless task but if you want to get some of the data back it may be possible. Just don't get your hopes up. Before you use one of these you'll need to acquire another working boot drive to boot to and add the corrupted drive to the system as a non boot drive.
Of course they always say to backup and that is good advice but in this situation I have better advice. Give each OS which you want to boot into it's own small physical drive...always. DO NOT try to put multiple OSes on the same physical drive. It may sound handy but it is a recipe for disasters like this. Also, don't put your OSes on your 900GB data storage drive NEVER EVER EVER. I don't care what excuse you want to hand me it is always a bad idea. Go find a few 20GB drives for your OSes; it will save you a lot of pain. If you have the cash these days I'd suggest getting an SSD drive for the OSes you use a lot but a HDD will do fine.
If you do this then you can easily remove all other drives before you install your new OS. This gives many advantages: it prevents OS installation program from messing with boot sectors it shouldn't be, it makes identification of the drive you are installing easier, it solves issues with the BIOS reordering the drives and the OS ignoring that order after it is installed which messes up the installation and it makes boot loaders completely unnecessary. When your OSes are all setup this way you can use your BIOS to select the drive you want to boot up (usually you press F12 during POST to do this but this may be different for your BIOS). Because each OS was installed thinking it owned the only drive in the system they will get the boot sector correct and load the first time with no additional effort on your part. They will accept that new drives have been added but even Windows won't care that these changes have been made and they will all live happily together.
The only real downsides to this method are that it may be more expensive (but you can usually find small drives for free because most people just want one huge drive and then they cry when it blows up), you need to open your case and unplug\plugin some SATA wires to install a new OS (I personally leave my case off most of the time because I'm always in there anyway), you cannot give the drives custom names for the BIOS drive selector menu (this doesn't bother me at all but maybe your BIOS is better at this than mine is and has this ability), and you are limited by the number of SATA ports you have (my mobo has 8 of them; if you need more than that then we need to start talking about VMs).
Maybe we should be talking about VMs anyway.