I can find no evidence that Aopen ever made this mb. and Google says it's an EPoX motherboard. We need additional input from you.
First, does your board have S3 Graphics UniChrome 2D/3D
or VIA Integrated Unichrome Graphic
Does it resemble this board?:
Epox has all but disappeared from the internet so I need for you to open Device Manager, double-click the VIDEO device, click the Details tab and give me the hardware id string that begins with PCI\VEN. Also, please tell me what the bios string is that appears in the lower left-hand corner of the monitor screen during the first few seconds of bootup.
Or..... you can click the HOME
button (upper left-hand corner of this page) and click the link to download the new (and free for a couple of weeks) DriverScan 2011 software. Download it, install it and run it. You should then be able to click a link to download a compatible vga driver for your motherboard.