Reinstalling OSX

I have MBP running OS X 10.10.4, Parallels 10.2.2 and Windows 7, SP1.
My MBP is running a bit slow and Apple's recommending a reinstall. I'm also intending to upgrade to Windows 10 sometime soon.

My questions are:

1) If I reinstall OS X, does it wipe out Parallels and Windows? If so, will that wipe out all of my Windows data? If so, how do I back up my Windows data (I do a Time Machine backup to an external hard drive every day)?
2) Is there a recommended order in which I do this? In other words:
- Choice 1: Upgrade Parallels and Windows before I reinstall OS X
- Choice 2: Reinstall OS X, then install the Upgraded Parallels (compatible with Windows 10) and then Windows.
- Do I need to first reinstall Windows 7 and then upgrade, or can I go direct to Windows 10?

 

Hello Infinitifi,
We suggest you to take a backup of Windows Virtual Machine before re-installing Mac OS X. You can do a Time machine backup and can restore it. Please refer to http://kb.parallels.com/8827
After re-installing Mac OS X, you can upgrade Parallels Desktop and Windows Virtual Machine on your Mac. You can directly upgrade Windows 7 to Windows 10 as suggested at http://kb.parallels.com/122884