[unknown filesystem, grub rescue>] after transitioning from dual boot to single boot

I had Ubuntu 10.04 dual booted with XP (two hard disk partitions) and I decided to reinstall Ubuntu 9.1 over both onto a single partition. I now have the following message:

error unknown filesystem
grub rescue>

I know that the basic problem is that grub is looking to an old location from which to boot Ubuntu. I just do not know how to edit the grub command to look for the reinstalled 9.1 and boot to/from that.

I have spent some time and gotten an idea about what I have to do. The following was taken from linexquestions.org and helps me understand the problem:

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When you dual boot a system with windows being one of it, the boot sector is modified by linux & a pointer to the grub.conf file is created (pointers to ntldr i.e windows bootloader is removed in the process).

Grub in turn knows, where to look for window's boot files & linux boot files. & redirects BIOS as per the choice made by user.

Now..... U deleted the liux boot partition & in the process deleted grub.conf.So when the pointer tries to find grub.conf it's unable to recognize even the FSystem,leave aside loading grub.conf.

& So the same it says:-

GRUB Loading.
error: unkown filesystem
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I just am not sure how to go about making the fix that is needed.

It can't be that hard of a fix and I know someone else has no doubt run into that after moving from two or more partitions to one. I would appreciate hearing from you who have dealt with this before.

Thanx