Yep, Windows 7 will break your GRUB. You can get it back like so:
1) Boot off the LiveCD
2) Open a Terminal and type in the
following commands, noting that the
first command will put you into the
grub “prompt”, and the next 3 commands
will be executed there. Also note that
hd0,0 implies the first hard drive and
the first partition on that drive,
which is where you probably installed
grub to during installation. If not,
then adjust accordingly.
> root (hd0,0)
> setup (hd0)
Reboot (removing the livecd), and your
boot menu should be back.
Check The How-To Geek's guide for more details, in case you don't see Windows in the boot menu after this configuration.