|See help and support for disk clean up. Run that first.May have many temp files in other programs too like firefox that you have to delete cache files and maybe games.|
Fragmented files are not bad and don't really take up a lot of extra space. In Windows you can't prevent fragmented files. It is part of how Windows works. You can use defrag often to help reduce them.
You can then look at deleting unused files, using compression on the drive may help, uninstalling unused programs may help.
Why did it take me over a year to phone in a problem to ATT?