Computer Woes?

Can anyone explain what is going on with my computer. It keeps ditching information eg sometimes when I start up it fails to load the keyboard, other times does not load my printer. It seems takes for ever to start up. (I have run antivirus scans, deleted temp files etc). Is something wrong with system and can I do anything about these errors (apart from trashing the computer). I am not an expert on computers so please nothing too techanical