Setting up mirrror raid on a Gigabyte GX58A-UD3R mobo

Download the raid manual from Gigabyte. It has step-by-step instructions. Beside that: a raid1 is useless for a desktop, because it will mirror all viruses and deleted files as well. Just get synctoy for free from Microsoft and backup your data frequently.

Put the hard drives in ports 8 & 9 (Gigabyte ports) and start reading at page 93 of your manual. I'm assuming you have your SSD in the Intel controller so let's leave that alone as it currently works.

Your manual -> http://download.gigabyte.us/FileList/Manual/mb_manual_g...

Windows virus problem does not make raid1 useless on a desktop. Replacing a failed drive and having the raid automatically rebuild is far simpler than restoring all your data from backup (and this can usually be done while the system is online and accessible). The OP should note that raid is not a backup and he/she should have one for important data.

If he gets a virus its going to copy itself to all the drives the pc is connected to anyways so it doesn't matter how the other drive is attached...

N_B_N is 100% correct. SCEA still needs a regular backup and I also recommend another backup you regualrly take off-site for data that he absolutely cannot afford to loose.

as for setting up the raid, while in the bios, set the ports the hdd's are on to raid; save and exit. Since you already have windows installed you may need to move the drives to a different controller than the one your ssd is on otherwise windows won't boot since changing to raid changes the driver needed. The controller the ssd is one should be set to AHCI.

While the pc is booting, you'll be prompted to press a key combo to enter the raid setup. ctrl-i or ctrl-f... once in the raid setup select the option to create a new raid. set the type to 1, add the hdd's, use the default values for the various settings, name the array, and then format it. Reboot when done and windows may want you to install the drivers when it boots up so have the latest ones ready.