To enter setup (Refering to the bios/cmos), press the Delete key very two seconds untill the bios main menu loads. You need to go to the menu heading - Boot.
If you added another hard drive to you're system the IDE (hard drive) it's jumper settings may not be correctly set. If there are now two IDE drives both the primary master & secondary drive's jumpers must be set correctly. You will ned to look at the white sticker on the drive for the correct jumper settings. Many primary IDE drives pin jumper is set as a single master drive with out a secondayr drive attached in the system. When you add a second drive the pin jumper one the master drive will most likely need to be changed to master with a slave. The second drive will also need it's jumper set as a slave drive. Once this has been adjusted you need to enter the bios & make sure you're primary master drive is set in the boot order. Most PC's boot order is as follows.
1st Boot device, floppy drive. (If one is connected to the system).
2nd boot device, CD-ROM drive.
3rd boot device, master IDE drive.
Please use the help of you're manual to guide you for these settings.
AOpen MX46L web site. http://download.aopen.com.tw/Default.aspx
You must set the three drop down menu's to get you're board's drivers & manual. In the first menu choose motherboard, in the second menu choose MX46L & in the last menu choose manual. For drivers, the third menu choose drivers.

Still heave more questions? Just ask.
Mike