Try shutting down all other programs you might have running, including those running in the background (for example, programs that show up in the notification area of your taskbar); some programs can interfere with the defrag process.

You obviously have too little storage space. The best thing you could do would be to install a second hard drive in your system. Move your Documents storage to a new drive, uninstall most of your programs and them reinstall them using your second drive as the program install location, and free up space on that system drive.

If things are extremely cramped at present, even defrag could be 'falling over' with not enough elbow room to work in. You don't say the size of your existing hard drive, but hey! 3% free space is 'aggravated cruelty to a Windows Installation'! You could damn near get JAILED for that

You could try running Defrag from Safe Mode.

That's possible, as defrag does need a certain amount of free disk space in which to temporarilly store the data it's trying to rearrange. However, you did say that after deleting programs you have 24% of the disk free, which should be more than enough "breathing room" for a defrag.

Turn off virtual memory [aka swap file, page file], reboot and try defragging. Turn virtual memory on again afterwards.

Run Defrag from a command prompt with the /f switch. This will 'force' the defragmentation even if space is low.

Not a bad idea in general, even if it doesn't solve the specific problem at hand here. The swapfile used for disk paging gets fragmented just like any other file; by disabling VM before defragging you can be absolutely sure that the disk space used for swapping/paging will get optimized along with the rest of the space on the drive.