How to make new partition on Bootcamp HD?

[owbp]

I have two 1TB HDDs in my Mac Pro, and since two days ago one is in whole El Capitan and other is Bootcamp, Win7. I want to make one partition on each disk, HFS Data on El Capitan disk and exFat Data on Bootcamps disk (to be for both OS').

In El Caps Disk Utility Bootcamp HD is greyed out and i cannot touch its partitions. Should i do it from Win or some third party app from OS X?
I wanted to ask first, because last time i messed with Windows' Utility on Mac, i somehow managed to change partition table and OS X couldn't read that disk anymore.

Didn't know should i ask here or in OS X sub forum...

Thanks!

 

[Mcmeowmers]

Try to never adjust partitions in windows. I can't answer your question but this might give you the right direction. Look up how to triple boot El Capitan and windows 7. (Yes, triple). The procedure should be similar. The steps you take depend on the age of your Mac and something about EFI and a tool called rEFIt? Or something!

 

[owbp]

@Mcmeowmers , thanks. I won't touch it from Windows. As i said in the first post, that messed with my whole HD last time i wanted to make small FAT32 partition through it. Ill look into rEFIt and what it does, and also see if GParted Live can be booted from DVD.

I didn't get this about triple boot though. I have 1tb OS X HD and 1tb Win HD. I want to make both 500gb and leftover space on both to make as a storage partitions (HFS+ and exFAT respectfully).
First (HFS+) is not a problem, 5 seconds in Disk Utility, but i don't know how to partition the second HD...

Maybe got to Boot Camp Utility, setup one more Win installation on the same HD i have Win now and then cancel the setup after the reboot?

 

[Mcmeowmers]

Windows doesn't like more than 4 partitions including recoveries but there is a way to get around it with that tool. The triple boot procedure describes how to get around the 4 partition limit.

I've only skimmed it when there was only one disk involved. I'm only guessing here but you might be able to partition from windows if it's on it's own disk. But please double check!