Strange things sometimes happen, one of them is a corrupt rpm database. This means that the computer tells you something is installed and it really is not.
Here is how to solve this problem.
First backup and then delete by doing the following command:
# rm /var/lib/rpm/__db.001
# cp /var/lib/rpm/__db.002 /home/nikesh
# rm /var/lib/rpm/ __db.002
# rpm –rebuilddb