Problems Compressing Friend's Hard Drive Win64

Hi! Yesterday, I tried to help a friend download some games online. Now, this friend has a recent version of Windows but I don't know which version. His problem was that his main hard drive is stuffed. He has a second hard drive, and it is almost empty. I tried to compress his hard drive the way I stated to somebody here. I don't know why, but the dialog box exited quickly. I then opened his hard drive in Explorer and tried to compress the folders, but I kept getting an error message on every file but don't remember what the message was. What could cause this? How do I fix it?

 

Unless I'm mistaken, compressing a data drive is one thing. Compressing C: is not advisable unless things have changed.

Pick up a budget HDD or SSD.

 

Okay. I'd better tell him the news.