CC-Issues

I have a problem with my comp and i really need your help. I had XP and Ubuntu in my comp in two separate partitions, but the partitions were somehow virtual meaning u could only see them when u were in Ubuntu side.
I wanted to see both partitions also from windows so on Thursday last week i decided to change the letter of the partition that had Ubuntu, I successfully did that. I went on to format that partition because i wanted to install Ubuntu 12.04. That's when my problems started, when i restarted the comp i got
error: Unknown filesystem
grub rescue>

This is very new to me, I have never come across such an error. I have done some research from the net and what is been recommended is to use an Ubuntu CD to do repair or an XP CD as well.
If any of you could be having a solution, please help.
Thanks