After installing Mountain Lion my bootcamp partition disappeared

Question

I installed Mountain Lion, and now I can't boot into bootcamp, and there is almost no trace of it to be found on my computer.  It shows up only in Disk Utility as "disk0s4", but it's greyed out.  It can't be verified or repaired.  Is there any way to fix this?

Answer 1

OK I'm wrong. You have a 30GB partition that's unallocated to either Mac OS or Windows (i.e. it is free space), so there is a story here that hasn't been told because the Mountain Lion installer would not do this. I'm going to guess at some point in time you used Disk Utility to delete a former Windows partition and make a new FAT32 partition that was bigger, and then reinstalled Windows. Or something like that...
The MBR partition entry for Windows has the wrong partition type code (0c instead of 07), and he partition isn't marked as bootable. So that's one problem.
Assuming nothing is wrong with the Windows bootloaders, the simplest way to fix this problem is probably Camptune or maybe iPartition (but I haven't used either to fix this particular problem and I'm not sure how smart they are). Neither are free.
The next easiest, which is free and easy but there is no GUI for it, is to use fdisk from command line to fix the above problems with the MBR. The notes in [ ] explain the steps, you don't type them, just the first part of each line, followed by enter/return.
sudo fdisk -e /dev/disk0
e 4     [edit 4th partition]
07      [partition type 07 for NTFS]
n       [edit in LBA mode]
875673600    [starting LBA for Windows partition]
101099520    [size in sectors for Windows partition]
flag 4
quit        
y            [confirm writing the MBR to disk]
Reboot your computer.
This instructions only work for the specified disk, for others to replicate, you have to know the correct start LBA and number of sectors, which can be found from either the earlier gpt or fdisk commands listing the partition entries.