Administrator Identity - Dell With Windows XP Professional

Dell with Windows XP Professional on it and 160 GB hard drive. When I got the computer home I went right into the Administrator Identity and began to use the computer. I was thrilled with it, so much harddrive and 512 MB Ram. After I had put a lot of my data on the computer I thought I might try another identity for other uses. So I went in to create a new identity. When I had finished with the new Identity the original Administration Identity that I had been working with for months no longer existed. After much consternation I did a system restore and got my original identity back. But what I want to know is how can I create a new identity without losing everything in the original Identity and I realize I should have gone on through Administrator to create the first identity. The original thread for this question has been closed.