If I will transfer 1080i HDV to DVD disc for viewing on PC how many minutes will fit on a 4.7gb DVD disc.

If you're talking raw HDV, then about 20 minutes. However as the datarate for HDV is quite high, I'm not sure if a DVD-R would be able to play it back without choking.

Should you compress to H.264, then storage times owuld be similar to SD DVD, though I gather H.264 doesn't handle interlace at all well. Also you would need a poerful PC to play back 1080 H.264.

You can get easily 1 hour, and up to 2, of good-looking 1080i WindowsMedia9 (WMV) onto a DVDR.

It's also less demanding processor-wise than H.264.