Crash and Die by Dell

I'm working my way up to a computer decision. Like many people I can navigate my way around my computer and do the things I need to do. But any little complication soon leaves me flaying about for answers. I do most of my writing work on my laptop. No one used my laptop except me. Until a few months ago. My daughter is taking all honors classes so she does a lot of research on the net as well as designing power point presentations and other things for school. Before she and my sons always did their work on our Dell desktop. It's a great computer and I remember how thrilled I was when we first bought it.
Here's the problem. It's going on four years old and its soooo slow. I've tried all the gadget things to speed it up. All those clean up utilities that come with my Norton Security package, but still I can only pep it so much. The fragmentation is often near the crash and die mark. So I went to the computer guru at work and asked her for some advice. She told me, but I'm scared to do it.
She described my computer as being like a house. When you first move into a house, you organize everything into its place. As the years go by, you build clutter, things don't get put where they belong, pieces of things are lost and basically you have chaos and have lost your nice neat house. So how to you fix it? She told me to start all over. Take everything out of the house and reinstall with the disk that came with my computer. Yikes!
But what about what's on there? I have to save it else where or lose it. Yikes again. All my pictures, my documents, everything. It's rather frightening. What if I do it and I can a fast computer again but I destroy forever something I really need?
So I'm brooding over the pros and cons of speeding up that computer. It stop my daughter from guilting me into letting her use my laptop because it takes her so long to do assignments on the desktop. It will clear out all the junk my boys left behind on that machine before they got their own computers for college. But it might clear out some of my important junk. Hmm. Has anyone else every done that? I'm afraid, very afraid.
I think I'll go write and leave the decision for another day. I'm working on book four, the final book, in The Solonian Chronicles. This book is Brady's and Cara's story. Can his love heal her soul? Maybe, but it hasn't yet and the book is over half written.
Give me some advice about the darn computer.