Well, hard to say that everything is not corrupted unless you verify each bit. What file system are you using?

Partitioning I believe (if you don't format anything) is just rewriting drive headers and creating a new header at some new point on the disk for the next partition.

Obviously we aren't in the days of sequential files, so files are spread physically over the disk with space in between. I'm not up with the exact specifics on whatever the latest windows FS is and how it works, or how EXT works at that level, but it would seem you partitioned it at a point after the data ended.

That, or you haven't corrupted the inodes/pointers, so it appears that all the files are there, until you try to actually access that place on the disk. If the files existed in the space that the new partition is, then you're going to get errors. I suspect this is more likely, because inodes will exist in the first sequential bytes on the disk, while the actual file location could be anywhere.

Correct me if I'm wrong on any of the details here.