Windows 8 displays linux ext4 partitions as RAW

This says how to hide it: http://www.7tutorials.com/how-hide-or-dismount-partition-windows

And you can read those partitions in windows with http://www.diskinternals.com/linux-reader/

The problem is that Linux hijacks the Windows partition type code (EBD0A0A2-B9E5-4433-87C0-68B6B72699C7) for its own partitions, so when Windows sees the Linux partitions, it thinks they're unformatted Windows partitions. A solution has been available for about two years, but the libparted developers have been slow to put it into a release version. (It is available in the current development version of libparted, but few distributions have incorporated the fix, as of yet.) The solution is to use a newish (2-year-old) type code for Linux filesystems: 0FC63DAF-8483-4772-8E79-3D69D8477DE4. Currently, the easiest way for an end user to do this is to use GPT fdisk (gdisk, cgdisk, or sgdisk) to set the type code. You can do this with the t command in gdisk, for instance:

$ sudo gdisk /dev/sda
GPT fdisk (gdisk) version 0.8.5

Partition table scan:
  MBR: protective
  BSD: not present
  APM: not present
  GPT: present

Found valid GPT with protective MBR; using GPT.

Command (? for help): p
Disk /dev/sda: 126613504 sectors, 60.4 GiB
Logical sector size: 512 bytes
Disk identifier (GUID): 742677E3-2035-46A4-BA91-AB7898654602
Partition table holds up to 128 entries
First usable sector is 34, last usable sector is 126613470
Partitions will be aligned on 2048-sector boundaries
Total free space is 4029 sectors (2.0 MiB)

Number  Start (sector)    End (sector)  Size       Code  Name
   1            2048         1075199   524.0 MiB   EF00  EFI System Partition
   2         1075200         5074943   1.9 GiB     8200  
   3         5074944         6150143   525.0 MiB   8300  Spare partition
   4         6150144       126611455   57.4 GiB    0700  Mint root (/)

Command (? for help): t
Partition number (1-4): 4
Current type is 'Microsoft basic data'
Hex code or GUID (L to show codes, Enter = 8300): 8300
Changed type of partition to 'Linux filesystem'

Command (? for help): w

Final checks complete. About to write GPT data. THIS WILL OVERWRITE EXISTING
PARTITIONS!!

Do you want to proceed? (Y/N): y
OK; writing new GUID partition table (GPT) to /dev/sda.
Warning: The kernel is still using the old partition table.
The new table will be used at the next reboot.
The operation has completed successfully.

GPT fdisk uses its own internal type code of 0700 to refer to Microsoft's partition type, and 8300 to refer to the Linux type. Thus, changing the 0700 partition to use the 8300 type code does the trick. Just be sure to convert the Linux partition's type code, not the Windows partition's type code! Also, be sure to use w to save your changes.

This solution is superior to hiding the partition using Windows tools because it applies universally; if you need to re-install Windows or move the disk to another computer with another Windows installation, the Linux partition won't have to be hidden again.