We bought a LCD TV just before the announcement of HD. Will there be a box available to convert the picture to HD after release, just like the sky box for example, or do we have to purchase another TV.
The only means of viewing HD at present are via a Sky or Cable HD box....or a HD DVD player.
There are no Freeview HD boxes at the moment and unlikely to be until after the analogue TV switch-off in around 4-5 yrs time.
As Mattk says, if your TV is not HD ready, then there is no way via any kind of add-on that you can watch HDTV. It's just not physically possible, in the same way that you can't view a colour picture on a monochrome TV