If you have Windows Vista or later, you can use VPOP3 v2.6 or later
If you have Windows XP SP3 or Windows 2003, you can use any version of VPOP3 up to v7.1
If you have Windows 2000, you can use any version of VPOP3 up to v4.0
If you have Windows NT4, you can use any version of VPOP3 up to v2.4.0
If you have Windows 95, 98 or ME, you can use any version of VPOP3 up to v2.6.0
If you have Windows 1, 2, or 3.x, you can't use any version of VPOP3