ses102076,
Welcome to this superb website and forum.
Is it possible for you to return your iPAQ 3600, as it is a discontinued model. The OS on 3600 is Pocket PC (or WinCE 2.1). The Pocket PC MS Reader you have downloaded from Microsoft can only be installed on Pocket PC 2002 or later.
Yours can ONLY be upgraded to Pocket PC 2002, which will cost you some additional dollars, pounds. etc..
I found one from ebay.co.uk as below:
http://search.ebay.co.uk/3600-pocket...jsZ1QQfromZR40
But my sincere advice is that if you can return the 3600, get the cheapest iPAQ of the most recent model, this will protect your investment for another year or two.
Good luck.