check the modified date of a the system files?
some might not have been changed since installation. that said, installation date is not necessarily related to the age of the pc.
( minimum fuss - an all time favourite, Wed 27 May 2009, 17:38, archived)

I just went into C:/WIndows and there's a load of folders modified in December 2005, which sounds about right.
I'm going to go with that. Thank you.
( Neptune A dole queue dosser and foul mouthed chav., Wed 27 May 2009, 17:43, archived)