So, based on your scenario if it was me I'd run TestDisk and get my files first, then see if I could get it to repair partition.
I've never used but I gave you the link to Step-By-Step and if it was me after I ran the "analysis" I'd then post on their Forum for guidance.....maybe start with you want to get files then ask how to address your specific partition recovery needs.
Go ahead and put the link here to that Forum post....I'd be interested to follow.
If TestDisk gets your files and partition back...great. Note, the other util PhotoRec will get your files back as well...kind of a backup to TestDisk. Anyway, if the above works great.....if you get your files but it does not recover partition then you have your Sony DVD recovery disk which I'm guessing will recover/restore your PC back to factory install. Obviously, you'll need do all the Windows Updates, install programs, etc.
Good luck and post the link to TestDisk Forum.