Although you did say Windows Im going to warn you in advance that if you ever plan on using a Linux install and want it to work in there then make sure you buy a chipset which is recognized. if you don;t plan on using it in Linux ever than disregard this advice.
External TV Tuner boxes can work with just the monitor if thats what you need but will lack the option to rcord anything.
For Internal Tv Tuners I have had a good experience with Pinnacle.
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go for the pinnacle pctv pci internal tv tuner card. It is really good card priced at 2.7k with 1 yrs of warranty.
Apart from TV watching, it can record TV shows, can take input from your analog sources (like your miniDV, HI-8, Digital-8 handy-cams), and record it either MPEG and Mpeg4 (DivX) format.