Know what the power requirements are for the hardware you have installed or will install in your computer, check out these wattage requirements for the common computer parts:

• Motherboard 15-30 watts
• Low-end CPU 20-50 watts
• Mid to high range CPU 40-100 watts
• RAM 7 watts per 128MB
• PCI add-in card 5 watts
• Low to mid level graphics card 20-60 watts
• High-End graphics card 60-100 watts
• IDE hard drive 10-30 watts
• Optical drives 10-25 watts

You should add up your estimated requirements, add another 30% or so for safety and upgrades to get a rough idea of your minimum requirement. You should always go more than the minimum.

If you are into top of the line, heavy graphics, overclocking, bells and whistles, start with a 400 watt power supply at least.

Figure a typical HTPC system will be as follows:

• Motherboard & CPU 105w
• 1gb RAM 60 watts
• Mid level graphics card 75 watts
• IDE hard drive 30 watts
• Optical DVD Drive 25 watts

TOTAL = 295 x 1.3 = 383 watts total required for aour base HTPC system

The below Case would work perfectly for an HTPC system:

Broadway 204-4HA-BK 10-Bay ATX Computer Case w/450W 20+4-pin PSU (Black)