Here's some random stuff to clog up your hard drive. Or SSD. Or NVME. Or MMC. Whatever you're using.
Classic Windows Screensavers: A collection of oldschool Windows screensavers including 3.1, 95, and XP, among others, all verified to still work on Windows 10. Yes, the maze one still works. Check out ME's windows.scr, that one's unironically cool even by modern standards.
Classic MS Paint: The old MS Paint from XP and earlier that was so simple. In newer versions of Windows, you can either replace your existing C:\Windows\system32\mspaint.exe with this one, or name this one something else and add it alongside. Works fine on Windows 10