I have a hard time findng your computer on the Dell webste. I'll keep looking.
But I did see that it has a 400MHz processor in it, so I think my thinking is right:
The largest hard drive you can put in it is 128GB (120GB more common). It's probably an IDE drive, but 2.5" or 3.5"?
Is it a laptop or desktop computer. And what OS are you running? Windows XP SP3?
It does have a 400MHz processor in it. It's a desktop.
Windows XP SP3.
Could it be easier to add a 2nd drive or an exterior drive?
Could there be compatibility issues by increasing the hard drive from 6.4 GB to 128GB?