URGENT: Marvell Virtual Cable Tester: How to test cable category?

My mobo (Asus P5WDG2 WS Professional) comes with two Marvell gigiabit LAN ports, which allows the user to run the Virtual Cable Tester (VCT) control panel/application from Marvell.

One of the things I understand it's supposed to be able to do is report the speed capacity of the cable being tested: 10 / 100 / 1000 for 10 mbit, 100mbit and 1 gig respectively. But no matter what cable I put in -- even those clearly marked Cat 5 -- it ALWAYS reports 1000, implying (it seems to me) that it merely reports the speed setting of the connected device, in every case reporting 1000 because both these ethernet ports are capable of gigabit speeds!

Is there any way to do what I want, which is to determine cable category (since too many of my cables aren't properly marked)?

I need an answer as soon as possible, as I'm right in the middle of installing someone's networking system and I need to get this working right away!