If yu put your hard drive in another computer as a slave you should be able to get your data back. If you try reinstalling the operating system first you will surely lose the data. The first thing to do is get your data. Reinstalling the OS is not that hard. If you lose the data your stuck.
If you dont have another computer or dont know how you should find a local service. When putting the drive in another computer as a slave you can easily see the drive and its contents. It easy to move/copy off that data and reinstall the OS.
The more you "play" with the drive the bigger chance of a data loss.
The original is windows?
If it is and your only other pc is a mac you will want to take to a shop to be sure you have no issues.
The idea is to mess with the original as little as possible to keep the original data.
I am not sure what they actually charge. I dont see that much ; )
To be honest computer support is normally $60 a hour. One hour minimum.
I have upgraded many computer from 7/8 to 10 with a full windows 10 disk with no issue. BUT people doing the free update from 7/8 seems to be a disaster. My 2 cents.
Just checking in