If I delete any of my digital desktop wallet and of course without any digital coins stored in them, Will my hard disk become spaced out of all those GB taken by the blockchain stored in my computer?
If you're concerned about disk fragmentation, you can run a disk defragmenter. In Windows Vista and later, this is done automatically if your PC is on overnight. If you're using a recent version of Linux, (if the filesystem uses ext2 or better) this isn't necessary either. If you're using a solid state drive, this won't help, because it doesn't have the long seeking times of spinning hard drives. This article tells you how to start the disk defragmenter on Windows manually.
In general, it doesn't matter very much.