I have had a similar problem like this before with two NTFS partitions on a very big hard drive, and they were not seen by WinXP. Well I was a bit fortunate as I still had a back up and thus did not loose anything.
Since then I always put a small FAT32 partition first and the REST in NTFS. I have never had the Problem again.
If you have to re-partition, you could create the first 20GB for instance as FAT32 and the rest as NTFS.
Good luck in trying out the suggested tools to retrieve your data.
