Saw a prison documentary recently and all the TVs (CRTs) there were clear plastic. It wasn't mentioned, but I'm pretty sure it's so the inmates can't hide stuff in there...
That is correct. I don't remember who, but one of the tech vloggers I frequently watch on YouTube posted a video about one of these a few years ago. They also don't have any built-in speakers (Or if they do, they've been disabled), they're designed to only be used with headphones. This was to prevent prisons from being disrupted by the sound of blaring TVs.
Anyway, back on the original topic...my first inclination was that it's actually Windows 2000 or Windows ME...but now I'm thinking that it is indeed Windows 98. The color of the wallpaper more closely resembles that of Win98 (Kind of a greenish-blue/teal color), whereas Win2K and WinME had more of a slate blue or cornflower blue. If the image were a little more clear, and assuming none of the default display settings were changed on the computer in question, I would be able to potentially at least confirm or rule out Win2K, since there are subtle differences in the default fonts it uses for titlebars, taskbar, etc. when compared to Win9x. It wouldn't help much to discern between Win98 and WinME though without seeing video footage of the computer being used outside the IE window.