Possible to Hide Mac Partition When in Windows?
I'm not a windows guy, so the steps are probably different but this SuperUser question asks how to disable a partition under Windows XP. The steps may be similar under Windows 7:


  You could remove the drive letter
  assignment for the specific
  partition(s):
  
  
  Go to Control Panel > Administrative Tools > Computer
  Management
  Expand Computer Management (Local) > Storage > Disk Management
  Right click the specific partition you like to hide and select "Change
  Drive Letter and Paths"
  Select the drive letter shown, click "Remove" and click "OK"