To maximize your chances of recovering data from that disk, be careful to not do anything that would cause a write to the disk. I am not familiar with "gpart", but it sounds like it might only write to the mbr (i.e. to fix the partition table). In principle, that won't affect any data, but think twice before doing **anything**
If the data is really important, then consider making a clone of the disk before trying any experiments.
1. How did you delete win 7?
2. When installing XP, did you make any selections to tell the installer how to partition?
3. Post the complete output from GParted---i.e. the list of ALL partitions, types, and sizes