Defrag free space issue

I have pulled almost everything off my computer and when I go to defrag it, it indicates that it needs 15% free space and it indicates that I only have 11%. How can this be, when nearly everything is off of it? Is there something else I need to be looking at?
Thank you for your assistance.

 

Have you also used ccleaner to clean out old junk files?

http://majorgeeks.com/CCleaner_Standard_d5125.html

How large is your hdd?

 

Did you clear your re-cycle bin?

 

Yes, I run CCleaner each week and emptied the recycle bin.
Any other suggestions?
1GB ram. Is that what you wanted to know?

 

No, not interested in amount of RAM. theefool was asking how large is the hard drive in the computer.

 

Capacity: 37.2 GB

 

theefool was on the right track as that's a small harddrive these days and fills up really fast. Use TreeSize Free to find culprits. Delete restore points except the last one if your machine has no other issues. Also, get rid of the hiberfile if you don't use hibernation by going to 'power options' and disabling it.That alone takes up space as much RAM that you have.

 

I downloaded the TreeSize.
11,474.8 MB documents and settings
8,919.3 MB windows
5,603.5 MB old hard drive
2,797.4 MB program files
1,534.5 MB [files]
475.3 MB I386
465.0 MB MSOcache
72.8 MB drivers
13.3 MB options
10 MB my downloads
The rest are minimal or 0.

 

Double click the top line to get further details in 'docs and sets'.

 

31,371.1 MB C:\ forgot that