my second Hard Drive Partition suddenly became ''RAW'' File system.

Good day friends, Please I need urgent help. My second hard drive partition suddenly became inaccessible and now shows ''raw file system.'' I can no longer open it nor do anything with it. For long now, my system has been dual boot of windows 7 and xp. This problem drive is where I have my xp and also d drive I use as my backup drive.. the data I stored in it has gotten to very reasonable extent remaining about 14gb or so out of 142gb. Just all of a sudden it started looking like a usb drive that has been corrupted and won't format. If I try to open it, it says ''D:\ is not accessible; The file or directory is currupted and unreadable'' the worst thing is that I can't even do system restore, it keeps sayin ''there was an unexpected error; the parameter is incorrect. (0x80070057) system restore will now close'' each time I try to use system restore. . Before this thing hapnd I tried to activate ''bitlocker on the drive but later changed my mind and didn't go ahead. now this has hapnd.. Please Ihumbly need urgent help as all my valuable data and documents reside on that drive. I don't want to format it yet and cos I do not hav any recovery ware that can help me recover my important files. Please can anyone kindly help me on what to do. Thanks so much in anticipation.. Happy new year.