Help me get data from failing harddrive

I just came back from a trip and my laptop suddenly took ten minutes to boot and then starting acting very very slow. I fear I may have dropped laptop and damaged harddrive. I also found that the all data partition part of my 640 GB hard drive became inaccessible to me. Explorer would freeze up and crash when I tried to access my data partition. My Data partition has 500 GB of data I want to retrieve. I tried putting the 640 WD scorpio blue drive in a hard drive enclosure but the 500 GB partition partition says location is not accessible the peramiter is incorrect. A microsoft windows popped up saying I need to format the drive before I can use it. I clicked ok but then quickly thought better of it and turned off computer afraid it would erase my partition. I turned my PC back on and opened disk management from manage my computer and I see my data partition listed as healthy 500 GB logical volume but it's file system says RAW instead of ntfs. Is this right? Disk properties would not do error check; it said windows can't access the disk. I also tried reinstalling windows on the primary non data partition of the 640 GB drive but each screen was taking ten minutes to load and the install wouldn't take.

Anyone know warranty options on this drive? I bought this WD 640 GB drive used from ebay about 6 months ago.