Yesterday night I properly shut down my laptop, but the next morning when I opened my laptop, I found that two of the drives were missing.
I checked Disk Management and it said that there was "90GB of free un-allocated space available". I created a partition in the available free space and consequently lost all my data.
After that I tried to recover my lost data, but was only able to recover 10%. After 2-3 hours, I saw that the the partition that I created earlier was missing again. I also checked Disk Management and saw the same thing as earlier.
Now I am wondering whether there is a hard disk problem or OS issue. I am using Windows 7 Ultimate 32-bit and my laptop is a Lenovo ThinkPad R61. How can I fix this problem and prevent it from occurring in the future?