It doesn't really matter that they are installed on separate drives, but if you are using
grub2 then that will be the bootloader for all of the operating systems. You need to configure
grub to 'know' what each of your operating systems is and which partition it is on. This is accomplished by using the
update-grub command, which automates the process of updating
/boot/grub/grub.cfg. I am assuming that you already have
grub2 installed, since you tagged your post with that.
First, create a bootable USB or CD in case you render your system unable to boot to
Xubuntu after reinstalling your
Windows drive. You have probably already done this in order to install
Xubuntu in the first place.
Read this Ubuntu wiki page to determine if any special factors apply to your system.
After you put your windows drive back in, you may experience the problem that the system boots straight to
Windows and does not offer a
grub menu to boot to
Xubuntu. This is because you have a boot partition on each drive. Follow this or this to repair your
grub to be the boot partition. Then:
- Boot into
- As root, run
update-grub. This should automatically detect your
Windows partition and add it to the boot menu.
- Reboot, and you should see a menu offering which operating system to boot.
If you have problems, make sure you have made some kind of bootable media first so you can repair. Post your issue back here along with the output of
fdisk -l and the contents of