All this is assuming you can still boot into Windows 11/10 in a regular way. If you cannot, the only way is to use a bootable USB drive. You can then use the advanced recovery. Reset Windows Format ...

Microsoft (NASDAQ:MSFT) releases old source code. MS-DOS and Word For Windows are downloadable (but don’t call them ‘open’). The Computer History Museum (CHM) hosts the files for us, calling them ...

How do I format a hard drive? A computer hard drive stores your files, allowing you to access them at any time. The majority of the time, you want these files to remain stored properly and safely.

Is your C: Drive NTFS? If so DOS cannot access it. If you want to reinstall XP or even Another OS it will let you format/delete the partition in the installer, atleast for every OS I have used.