One other approach - a bit safer.
Install a fresh copy of Windows (preferably to a different drive or partition). If the same drive/partition, choose to install into a different directory (like c:\safeboot). Not a bad time to purchase a second hard drive, IMHO. Do not access anything on the infected drive/partition (unless you install to the same drive, in which case you have no choice).
Install your virus scanner and update to current definitions.
Update Windows with all current security patches (windows update).
Scan & clean. Note: by booting to an alternate Windows, you can effectively clean system files.
Check the cleaned (or quarantined) files. If any seem to be critical windows files, copy a replacement from your safe windows to the "bad" one. (Alternatively, after cleaning, do an upgrade install of Windows on top of the "bad" install. As before, update with all security patches & make sure your virus scanner is installed and up to date).
This is why the TCO for Mac (or Linux) is probably way lower than for Windows.