Most problems come under two catagories: hardware or software.

In the instance of software problems, it is most likely that no components will require replacement. If the problem cannot be sorted out directly then it could be the case of obtaining the latest software drivers. In some extreme cases a complete reinstallation of the operating system could be required.

Hardware problems are usually more fundamental. The computer will either not switch on or a particular component will not work. For example:- floppy drive will not respond, "boot device not found" or modem not responding, etc.