I believe it is but someone else will have to give you the directions. There
is also a grub repair disk you can down load and burn called Supergrub.

I messed with this for a while, when 9.1 took liberties with my
MBR and stuck grub in there before I knew how to avoid that.

SuperGrub will install grub (V.97) to a bootable partition but it
won't set/edit the configuration for you. You're on your own
for that (via rescue disc, maintenance partition, etc).

I am a newbie, but I had a similar problem. I updated the kernal and a
bunch of other things at once then computer asked to reboot. So I did!
But then it kept trying to reboot over and over with no success. I'm
using ubuntu 9.10 by the way. So what I did was put in the ubuntu 9.04
install disk but went into the live section with out changing
computer. I then went into gparted and executed a check partitions and
auto correct errors, on both win vista partition and Linux partition.
Once complete, I closed all apps, took out cd and then rebooted.
Worked perfectly for both operating systems. Boots up fine now.