I'm getting two different computers with that model number. One is a Latitude C600/C500 laptop and the other is an Inspiron of some sort. Do you see a Service Tag on it? See
If it's the Latitude then there is no hidden partition.
To rescue your files you might try the AVG rescue disk:
I think it has a file manager on it that should let you copy files to a USB or burn them to a CD.
The Ultimate Boot CD is also handy:
One thing that happens to old laptops is the battery drags them down so try removing the main battery and see if it will boot.
Perhaps in Safe Mode. (Reboot and when you hear the beep, see the Dell logo or it mentions F8, Start tapping the F8 key slowly. Keep tapping until you see the Safe Mode menu and select the top option.)
Another common problem is hard drive failure. It's a moving part so subject to wear. The Ultimate Boot CD has several Drive tests tho I think you have to know who makes your drive which it will probably tell you.
Laptops also have small air vents and are subject to overheating if these get clogged with dust so take a vacuum clean hose and try to suck out the dust from each vent.