...Windows ME . . . ??? I can buy a compatible 80 GB hard drive and a dvd/cd read/write drive to replace the read only drive in it now.

If I do this - and have all that extra space - will I be able to load a newer version of windows on the old computer???

I know that I could probably get more by buying new - but if I can salvage my old machine, I would like to - I like the packaging it is in, the size - and the sentimental value of the nearly 10 year old computer.
I think I have Pentium III with 600 MHz.
Purchased 1999 or 2000.
256 MB RAM