Computer help: Windows 7 related

I am hoping that a computer guru who knows win7 can help me out because I am at my whit's end.

Background: I recently installed win7 ultimate on my laptop. Windows made a folder on my C: drive called Windows.old and it contained all of my important files (pics, movies, music, etc). I also have a desktop on win7 ultimate. Both pc's are on a homegroup.

My Objective: I want to transfer the important files from my laptop to my desktop through the network (homegroup) but I am having trouble moving a large amount of data. I can only move small file sizes. I keep getting an error message that says:

There is not enough space on Users. You need an additional x GB to copy these files.

I don't get it. Any ideas?