I broke may Mac Pro

[PrzemekLegion]

So, I have this Mac Pro server Xenon Quad Core beauty, silver aluminum, 25 kgs in weight, all the bells and whistles...). Since I need to run some Windows software, I had bootcamp install Windows on a separate disk (there are four slots in the HHD bay). I plainly ignored the message that ONLY Windows 7 could be installed, and this resulted in a failed bootcamp install. Upon this, persistently, I sucessfully installed Windows 10, and now my Mac Pro can only regognise Windows systems - no original install DVD's or Carbon Copy copied disks of my other Mac OS X machines will be recognised as bootable drives.
PLEASE, PLEASE PLEASE: how do I make my Mac Pro work with Mac OS X again ...

 

[smoothmove]

You installed it on a separate drive.

Goto system preferences and then STARTUP DISK.

Select your MACOS drive for startup drive