Grub and MBR

[BravoCharlie]

If you are formatting the C: drive you will of course need to re-install
Windows and that will write to your MBR, then when you install Ubuntu it
will overwrite the Windows boot loader in the MBR with Grub and
automatically add an entry so you can boot Windows as well. Depending
on what partitions you already have set up on your C: drive you may
want to run a partitioning tool to reduce the size of your Windows
drive to leave some free space for Ubuntu to create it's partitions.


-- 
BravoCharlie