How can I completely wipe an infected PC and reinstall Windows?

During Windows Setup, partitions are simply separate sections of a physical drive. On the screen asking where to install Windows, you can select each partition belonging to the target drive and choose Delete until it shows as one block of unallocated space. Then select that unallocated space and continue. If the computer has multiple drives, disconnect the extra ones before installing so you do not accidentally erase the wrong disk. Reconnect them afterward and wipe them through Disk Management if necessary.

First disconnect the computer from the internet by unplugging the network cable and turning off Wi‑Fi. Using a different computer that you trust, download the official Windows installation media and create a bootable USB drive. Start the affected PC from that USB, choose a custom installation, and delete every partition on the target system drive. Select the resulting unallocated space and let Windows create new partitions automatically. This erases the old installation and its files, so make absolutely sure there is nothing you need first.

If you are uncomfortable identifying drives or booting from USB, a reputable repair shop can perform the clean installation safely. Replacing the drive is usually unnecessary for ordinary malware, and flashing the BIOS should not be the first step. If the infection involved other storage drives, wipe those as well or leave them disconnected until the fresh Windows installation is complete.