You probably will not be able to backup any files if it does not boot to the OS. You can take it to a qualified computer technician and have them try to recover the hard drive. You should know that this will not be cheap. Unfortunately nobody thinks to do a backup of their important files until something goes wrong. Good luck!

This is a tough one, if the computer turns on and passes the computer checks and does not load the OS could mean that the hard drive is failing, which is where your data is. If this is the situation I would put in the OS disk and run a repair, to see if it fixes the OS info and runs it, but you said you dropped it which could have damage the internal workings of it and there is no fix for that, time to get a new hard drive and be more careful.