Macbook pro fell from the dining Table

If the machine will run, open Disk Utility, select the hard drive, click the First Aid tab, and check the SMART status of the drive near the lower right corner of the DU wiindow. What does it say?

That's far from an infallible indication that the drive is fine, but at least it's something positive.

Run the Apple Hardware Test from the Lion Recovery partition.

Run the Repair Disk Routine in Disk Utility, also from the Recovery partition.

Post back with results.

If you don't have Lion, ignore my prior post. Run the Hardware Test from the Applications disc that came with your computer, and boot from the Snow Leopard installer DVD to run the disk repair routine in Disk Utility.

No, you should only upgrade your OS when everything is running smoothly. Upgrading a wonky OS is likely to result in a failed or faulty installation and a computer that doesn't boot or runs badly.

Instead of running the Repair Disk routine in Disk Utility, you can start up in Single User Mode and run fsck:

http://support.apple.com/kb/TS1417

That will repair the hard drive directory if the drive is in good mechanical order, possibly resolving the ballkiness mentioned in your first post. If the drive has suffered any damage in the fall, directory and file corruption may return quickly. I recommend backing up the hard drive ASAP if the machine will run long enough to do it.

You can try running Apple Hardware Test without the Applications disc. If you have a unibody MBP and your hard drive has never been reformatted, it may work:

http://support.apple.com/kb/ht1509