Given that the problem is with the FAT32 filesystem on the partition itself, i.e. not a problem with the partition table or with the rest of the system, my best bet would be to do the chkdsk under Windows (from the disk manager).

You had that even in your first post "it recognizes the N900 as Removal Disk G and H but I can't explore." Doesn't it let you check the file system for errors?