Yes, there's a gotcha: Windows will clobber the master boot record (or MBR) which contains the early boot code used to bring up a system.
>Save the MBR as it exists now (le link
, in this case you'd need to re-run update-grub
to get Windows to show up in the boot menu)
>Boot into a linux disk of some sort, either a disc meant for recovering GRUB(2) (le link
) or using the Ubuntu installation disc itself (le link