First, a little clarification for future reference. The term memory refers to how much RAM is in your PC. What you're talking about is disk space.
We would need to be able to look at the files on both of your systems to understand why your laptop has less available disk space than your desktop.
Have you tried emptying the Recycle Bin on both systems?
You could try running this program: windirstat
on both systems. It will help you find which folders and files are using the most disk space,