A 200-watt power supply is considered basic. It will also have a firm, crisp 'touch' and the key caps will be firmly attached to their posts. Most better keyboards come with their own manufacturer's warranty. You should expect to find it among the pa-pers that come with your new machine. Mouse A mouse or other 'auxilliary pointing device' used to be an option.
Mice come in both 'serial' and 'bus' versions.
The bus model comes with its own adaptor card that plugs into one of the expansion slots inside the computer. Both usually come with a selection of driver and accessory software. As with most other parts of your computer, you get what you pay for. Ask your dealer. Buy the biggest screen you can afford, but be aware of the price break-point.