So you installed the grub to the MBR and all partitions? If you were running ubuntu installed within windows (i.e. using wubi) then you need to get the windows bootloader back on the MBR of your drive.
But you'll still have issues as the bootsector will also have been damaged, so you need to recover this.
It's possible to do this with the windows dvd the commands are
The bootinfoscript is really useful, but if you can't get hold of an ubuntu boot cd, then you'll have to use the windows repair option.
Here's a microsoft link for more info: http://support.microsoft.com/kb/927392