I'm a little confused, but it almost sounds like it might be a RAID 0 setup using 2 x 500GB hard drives. When you initially boot the computer, do you see a black screen that says something like "Press <Ctrl-I> to enter Configuration Utility"?
Also, please go to Start, type in diskmgmt.msc and open the program that appears at the top of the list. You can attach a screen shot of the window opened by pressing the "Print Screen" button on your keyboard which is on the right, just above the number pad. Then go to Start -> All Programs -> Accessories -> Paint. When Paint opens, press the icon at the top that says "Paste" which will paste a copy of the print screen we took earlier.
Now click on the Save button at the top, change the file type to JPEG (.jpg) and save it somewhere you remember. Then please attach that to your next post.