I've been helping my good friend through an issue where a newly purchased 150Gb hard drive is only showing 80Gb after using Norton Ghost to copy data from a dying 80Gb hard drive.
Even after formatting the entire drive, it still only showed up as 80Gb - even on other computers.
After doing some searching on the net we realised that the "Ultimate Boot CD" had a utility on it called HDAT2 that could reset the size of the hard drive to its original size.
The first question in HDAT2's online FAQ deals with resetting the size of your hard drive to its default using this utility.
Very useful if you ever get stuck like this!
On a side note, the BIOS on Dell's laptops are crippled! The only thing you can change in them is the boot sequence! Argh.