Reinstalling a node puts a fresh copy of its operating system on it. A reboot leaves your data alone; reinstalling deletes everything already there: every file, every setting, and any licensed software on it, like RDP, MS SQL, or BitNinja. Save what you want to keep before you start. Create a snapshot or save the node as an image first, or make sure backups are already on.
Open the node’s Actions menu and click Reinstall Node. It is not offered while accidental protection is on, so turn accidental protection off first if it is missing. Confirm, and the reinstall starts. It blocks every other action on the node until it finishes, so leave it alone while it runs. Once it finishes, the node is on its fresh operating system, with none of its previous data. Connect to it as you did when it was new, then restore what you saved. If the node stays busy for a long time, see Troubleshooting node actions and lifecycle.
To reinstall a node through the API instead of the portal, see the node-action operation in the API reference.