Yes, You need a tuner. Have a look here.
I have had a media centre PC on both XP and W7. The software was with the installation disc, but if you explore the link I think the tuner supplier has software. You can burn dvd's but if that is your main reason, it would be easier to buy a Freeview DVD recorder with HD and disc burning facilities, as the PC coding is not as easy as that of a DVD recorder..