System loading error

[YasinG]

I tried to install XP but it couldn't be installed because there are no compatible drives on my hard drive .. I don't understand what is that or how can i make a drive compatible.
Then when i tried to boot normally it shows me a black screen and the words 'error while system loading' or something like that.
Now I'm stuck. I'm on my live USB flash drive now.

[YasinG]

Guys any help ?! My system has been down for a day now ..

[YasinG]

I fixed it .. !!
Just did this :
sudo grub-install --root-directory=/mnt /dev/sda
And it worked ..
Now all i need is to install windows .. so i still need help .. but thats a different topic.