For VPS Windows server 2019:
Please go to Server Manager -> Tools -> Computer Management -> Disk Management
Or you can type the command Diskmgmt.msc :
> Press Enter :
2. Right click on drive C as shown in the image and choose Extend Volume
> Click Next
>Click Next
>Click Finish
> So you have successfully extended the hard drive from 25GB to 30GB
For Windows Server 2012
It is very similar to the steps for Windows server 2019. You can see the instructions in this video: https://www.youtube.com/watch?v=VyK4S3N-wFA