Due to the flooding in Thailand, Dell have a announced they are to transition all their desktop systems to Advanced Format hard drives (see Dell article number 408172).
This will probably cause issues with your captured OSD images. For Windows 7 deployments, Microsoft have issued a hotfix (here), but this has been included in Service Pack 1. Windows XP looks like it'll be a bit more complex to get working with the new drives. I'll be blogging more about this once we get our hands on the samples from Dell.
In the meantime, these drives are being phased in, and Dell warn that "multi-unit shipments may include both Advanced Format and conventional (512b) drives."