You can't use the IrDA that is built into the mobo. You still need to use a receiver that comes with whatever peripherals you buy.
But what's the point of infared? Line of sight stinks unless you need the range, like a PC that sits up next to the tv or something. There are plenty of RF devices around, keyboards and mice abound. I would suggest
Logitech for both, or at least the keyboard. Personally I prefer the MS Wireless Intellimouse Explorer over the cordless Logitech offerings.
Hope this helps.
BTW: range is about 6 ft.