XSFC

XSFC is a feather-light and portable application that you can use to reduce the size of files by compressing them into archives with the .xpack format. It also has a decompression feature.
The tool contains only the necessary and suffice options for accomplishing these tasks, which means that it can be used even by those who've never tinkered with an archiving tool before.

Compress and decompress files

The interface is made from a window that's just big enough to comprise four buttons for compression, decompression, the help file, and exit. It's evident that the program prefers to stick on functionality rather than looks, judging by the rudimentary appearance that makes it look like an unfinished software project.
All you have to do is find and select a file using the file browser, and let the application take care of the compression task. It automatically creates the .xpack item in the same location as the source and maintains the original name. The same rule applies for decompression.

Observations

Worth noting is that the original files remain untouched in both compression and decompression jobs, so there's no need to create backups prior to using this app. Unfortunately, it doesn't implement features for compressing multiple objects at the same time. Plus, you cannot change the output folder and file name.

No setup required

The program's not wrapped in a setup kit. Instead, you can copy the downloaded files to a custom directory on the disk or to a removable storage unit, in order to seamlessly run XSFC on any PC with as little effort as possible.
There are two files available, corresponding to the English and Italian UI language. Unlike most installers, the app doesn't modify system registry settings, so it doesn't increase the risk of OS stability issues. In order to uninstall it, you simply have to delete these items.

Evaluation and conclusion

XSFC worked smoothly in our tests, without triggering the operating system to hang, crash or indicate errors. It left a small footprint on system performance. However, we haven't noticed any difference in file size before and after compression.