The latest = after the best part of 2 hours, Windows tells me that C:\ is low on space and I should "click this" to free some up...

Installation therefore aborted, Revo utilised, all's well with Windows XP.

The area that's specified as being low on space is, I think, in Docs & Settings, Temp Files - would that make sense? I'm going to try the forums again but it's so "busy" there (as in, lots of info that's incomprehensible to me) :(