Many years ago the most expensive part of a computer system was the hard drive. So people were using small hard disks in their computers because they weren't affording large and expensive models. A small hard drive meant less space to store the data so as a solution there were many third-party utilities to compress the hard drive. What they did was to compress the data on the hard drive to take less space so users were able to store even more data.
As a result these utilities became very important because many computer users relied on them to get more space which determined Microsoft to add this feature in Windows XP. This way computer users became able not only to compress individual files but to compress entire folders and drives. It became easier to compress drives but unfortunately the compressing process took longer and was slowing down the system.
The important question in this article and its aim is to get an answer for the question "To compress your hard disk or not? ". The compress feature still exists in Windows XP but this don't mean that you have to use it so the answer is No if you have a large hard drive (larger than 30 gigabytes). In this case don't compress your hard drive.
Note that if you need to compress your hard drive badly this would slow down your system because accessing the system files will be a slow process. My expert advice is to not compress your hard drive as defrag is better and healthier.