Usually, the cover needs to be taken out before the Front Panel can be taken out. After taking out the cover, look for a latch/quick-release to free up the Front Panel. The Service Manual should give you detailed instructions.
The srvice manual does not have detailed instructions; there used to be really good illustrations on the packard bell support forum but since the takeover.............
The Mozart Chassis is all clips and slides, I can get one side panel off easily but can't remember how to get the other off, and there are no obvious screws. I know that the front cover unclips but can't remember the order or where.