Do not run or try to run any os with these drives attached, can make things worse.
If your other 500gb drive is seen in the bios the same your chances are maybe good for data recovery.
Take to drive recovery company if can afford it.
Time to google for sector hard drive image and clone tools. You will also need 1tb of space on another drive’s to image or clone to.
Better to get hold of some tools and read their manuals, than me writing here a full guide. Low level sector copying from one drive to another in dos. Then do the same for the other drive. x2 500gb = 1tb, read chosen software manual for full details.
If you chance diy you hope the drives are in good condition for low level copying. If not you will have to seek professional help to recover the drive data.