Grub boot loader has disappeared!

[Jared Buck]

I had to reinstall Windows on my dual-boot system because it was
running very slowly (likely due to spyware on the computer that my
spyware removers couldn't find).  When i reinstalled and booted back
up, the GRUB boot loader vanished.  I need to get back into Ubuntu so
i can transfer some stuff from there to my Windows half of the
computer.

Can anyone tell me how to get the GRUB loader back so I can continue
to dual-boot?

Jared