I’m not sure why you would do this to be honest, but if you’re feeling nostalgic for good ol’ Windows 98 and it's Windows 98 Plus! Themes, you can now get them installed on Windows 7. In addition to just the wallpapers themselves, blogger Manan over at I’m Just Being Manan
also managed to extract the mouse pointers, desktop icons, and color schemes, too. The four themes he has transformed for Windows 7 include “Jungle,” “Mystery,” “Baseball,” and “Travel.” Ahh, memories.
Manan also posted instructions on how to customize the various themes, too, in case you don’t know how. If you want to download the Windows 98 theme pack for Windows 7, you can do so from here…(but I sort of hope you’re only doing this as a joke!)