If you're facing the issue where the "Extend Volume" option is greyed out in Windows Disk Management, it's often due to the lack of unallocated space immediately adjacent to the C drive. This is a common limitation in Windows' native partitioning tools. Fortunately, third-party software like Partition Assistant can effectively bypass these constraints by merging partitions or reallocating unallocated space to your system partition. The process with Partition Assistant is user-friendly. After installing and running the program, you right-click on the C drive and select "Advanced" > "Merge Partitions." You then select the unallocated space available on your disk, confirm the operation, and finally click "Apply" to execute the changes. Importantly, this method safeguards your data by avoiding reformatting or reinstalling your operating system. Before proceeding, ensure you have backed up critical data, just as a precaution. Also, check that the unallocated space is located on the same physical drive as your C partition; extending volumes across different disks isn't supported. If there’s no unallocated space next to your C drive, you may need to shrink or delete adjacent partitions to create some. Remember, the process of modifying partitions involves some risk, so a backup is essential. For those running low on disk space, extending the C drive can improve system performance and prevent errors due to insufficient space. Another tip is to regularly clean up temporary files and uninstall programs you no longer use to maximize free space. By following the steps outlined and using reliable partition tools, you can effectively manage your disk space and extend your system drive without losing data or needing complex Windows reinstallations. This approach is suitable for both Windows 10 and Windows 11 users looking to maintain smooth and efficient PC operation.