143 MB is the size on disk - it is not related to how much (virtual) memory is used - if you don't use it, it's taking up disk space, but not memory.
Programs have a size on disk, and then they use memory when you actually use them - the amount used can vary depending on what you do - e.g. Word has a size on disk, and then when you load it, it takes up memory - the bigger and more complex the document you edit, the more memory it uses.
Deleting programs will not help your problem - it will free up disk space, but do nothing to free up memory.