In most desktop computers, only one side panel is removable in order to gain access to the inside. Once you remove this side panel, there will be a latch usually, that you slide to release the front panel. Sometimes, the front panel is secured by a couple of plastic tabs that you must push and release. In some cases, you must grab the bottom of the front panel and just yank it off with one firm pull (some Cooler master cases). Very rarely do they use screws to secure the front panel.