Will Disk Director mess up grub (the Linux boot loader)?

Hi,

I have a laptop with Vista and Ubuntu Linux. I used Acronis Disk Director to shrink my Vista partition and add three partitions for Ubuntu (two ext3 and one swap). Since I now are using Linux more that Windows I would like to shrink the Vista partition more. If I do that and add the space to one of the ext3 Linux partitions will I be able to boot using grub when I am done, or will Disk Director overwrite it so I only will be able to boot Windows? I have searched the forums but can't find anything conclusive. I want to be very sure before I do it since I need to computer for work and can't spend hours finding out how to get into Ubuntu again

I know Acronis has a boot manager, but I would rather use grub since it gets installed, updated by Ubuntu. Also, in a couple of months I won't need Windows on this computer at all, but in the mean time I would like to increase space for Linux.