Our ancient Videonics switchers is about to give up the ghost. Is there a way to make a switcher using tv tuner boards and a Vista machine?

The only thing I've been able to turn up is the Matrox and Tricaster editing systems, but that's way out of my ballpark...

I was hoping to cobble together something with -- I dunno... TV Wonder cards and switching / Video DJ software?

I've seen VidBlaster, but we're stuck with analog sources -- and USB is way too jerky.

Edirol is making same kind of product

Ok, so maybe I should be saying "Video MIXER", rather than 'switcher'...

Again, can this be done with a PC and composite/s-video capture boards? The PC doesn't have to record all three streams, just show a preview onscreen and record whichever stream is selected.

Currently I'm using VidBlaster in Trail mode. Hasn't been to jerky and my 3 video inputs come through just fine. Just need to get some graphics prepared and I'll be ready to hit the pavement.

Setup:
MacBook - Running Win XP via Bootcamp
Belkin USB 2.0 Hub
3x Roxio USB Analog converters
Shure 32a Field Mixer
DVCam Deck for Line record
2x HMC-150 handhelds
1x A1U wide shot
1x Comprehensive VGA Converter to S-Video
3x Sennheiser Announcer Headsets

Only problem is 320x240 video output until the latest version of Studio is released.