how to get my files back after format

Hi,

My computer is made from Dell with Vista windows. Several days ago,it is completely down and I do not know the reason, maybe virus infected. There are two partitions C (228GB)and D (10GB) disk in my computer. My files are saved in C disk. I once tried to use XP windows CD to format D disk, but unfortunately format C: disk (the format is not finished,I powered it off while it just started).
I have lot of important files saved in the computer. But I can not find any one after reinstal the Vista Windows on the D disk. Please let me know if you have a solution to get my files back.

Great thanks,