.cpr project files dissapearing

Hey guys.
Im desperate for help here.

Ive had some .cpr files dissapear recently off both my hd and my portable hd (backup).
Ive done every search of every corner of my pc and backup. Cant find them. I have no malware etc.
I realized today that windows 10 isnt compatible with cubase 7.5. This is the only potential reason i can find for this happening. I still have all the audio files, just the .cpr files are dissapearing. Im not expecting to get the .cpr files back (that would be a life saver though) but i at least want to confirm this is relevant before i throw my computer over a rainbow. Ive got .bak files but they are only from super early stages of the projects so theyre almost useless.
Ive already lost a huge amount of work and am scared to touch any of my other sessions in case it happens again.
Has anyone had this before?
Thanks in advance