The first thing to do is go into the Bios and see if the drive can be detected (F2)
If it detects the drive then loses the drive settings after it has been turned off the battery is no good, look at the page at the following link.
http://www.ari-service.com/bulletin/ib/0081ib.htm
AST RESEARCH, INC. INFORMATIONAL BULLETIN # 0081 1/27/99
Optimum Longevity from Your Notebook Battery
Care and feeding of your battery is an important part of notebook ownership and will reward you with maximum battery life.
If you are or know a competent computer user try this.
If after charging or replacing the battery you still have no joy you could take out the drive and with a IDE converter/connector install into a another computer to see if it can be detected, I WOULD USE AN OLD COMPUTER.FOR THIS.
If your data is very important you can send it to a company who specialise in data recovery (not cheap)
http://www.ari-service.com/default.asp
Due to a faulty batch I lost a 40gig Maxtor drive recently, I learnt a long time ago about the importance of external backups.