MailWasher Free 6.5.4 compatability

Hello I visited Major Geeks before but never joined the forum before. I'm trying to get MailWasher Free 6.5.4 to run with OutLook Express 6. Every time I attempt to run setup I get a error window saying I this program needs to run on NT version 5 or later. How do I get this to happen? When I go to OLEx properties > compatibility option is not available, and almost all other programs offer a variety of choices, however even with the other programs the only NT format available is Windows NT 4.0 (Service Pack 5) :confused