You don't need to convert mbr to gpt for install windows 8 or 10 and you won't wipe your whole hdd.
We have another way to install 8 or 10 to mbr partition
1) go to bios setting (by pressing F2 or F10 based on your mother board)
2)go boot menu
3) disable UFEI Mode
4) press F10 and save the settings
Now plug your win 8 dvd or usb and follow the process it's won't ask to convert MBR to GPT
We have another way to install 8 or 10 to mbr partition
1) go to bios setting (by pressing F2 or F10 based on your mother board)
2)go boot menu
3) disable UFEI Mode
4) press F10 and save the settings
Now plug your win 8 dvd or usb and follow the process it's won't ask to convert MBR to GPT