Have you considered getting one of these:

http://cgi.ebay.com/MCE-TV-Philips-7135-PCI-TV-Capture-Tuner-Card-XP-Vista_W0QQitemZ310087941005QQihZ021QQcategoryZ3761QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

OK, so probably not the best quality capture card on the market, but they do have the necessary built in tuner and they're as 'cheap as chips'.

... just a thought.

EDIT: Have a look here to see how the cheap MCE compares to the PDI/Sweetspot. I'm certain that you'll get a much better quality capture going directly into the RF on the MCE card as opposed to using a VCR to do the RF conversion.