It's not a property of the OS or the PC. It's a quesyion of having the right recording program. So it isn't in the specs of the PC, it's in the specs of the recording program you buy.
I would like a computer that can be used as a DVR also, if I can see the content in high-def 720/1080 as originally broadcast. I don't know if this is a reasonable expectation for a computer, or if so which ones. I'm thinking this always or never happens, because I don't see it in their specs. DVDs record at 480, and there's not a great selection of separate DVR units. PS- can the PS3 record in highdef?