How to compress entire drive C in Windows including locked files?

If I just set checkbox for compressing drive C in Windows Explorer, I will get numerous file sharing errors, because many files are opened when Windows is running.

Is it possible to compress drive in monopole mode somehow, so that it compress all files>

Solution 1:

DO NOT, I REPEAT, DO NOT DO THIS!!

Source: I did the exact same thing a year back and it renders the system entirely unusable. In my case, the process completed without any error, but when you boot, Windows doesn't create a mechanism to properly decompress the data and boot fails. You can compress other folders but leave out Windows and Program files at the least.

Besides, compressing might even mean slower performance depending on your processing power, since everything has to be decompressed every time (though it could be marginally faster if your I/O speeds are the bottleneck).