I've made no secret of my love for turning PCs into HDTVs. All you need is a tuner that pulls down over-the-air HD signals. I've spotlighted a few bargains in the past, but usually you had to wait on a rebate. Not so the KWorld PlusTV ATSC 340U, which Buy.com has on sale for $34.99 shipped--no rebate required!
The PlusTV is strictly an ATSC/Clear QAM tuner, meaning you need to use its included antenna (or your own rabbit ears). However, if you're a cable subscriber and your cable company broadcasts Clear QAM signals (i.e. digital cable without a digital cable box), you can go that route as well (though you may not get actual HD programming that way).
KWorld's tuner comes with ArcSoft TotalMedia, which lets you watch and record shows DVR-style. It should work with Windows Media Center and other media-center apps as well. The bundled software also lets you burn recorded shows to DVD.
I haven't tried this tuner myself, but I've seen only positive user reviews (including this informative one from an Amazon customer). There's still time to catch the Final Four in HD (go Spartans!), and you can do it for a mere 35 bucks.