If you’re dual- or multi-booting between Windows XP (using the classic interface style) and other Windows products, you may sometimes wonder which operating system you’re running at any given time because the GUIs of the post-Windows 95 OSes are often virtually indistinguishable. Yes, you’ll see a few giveaways, such as My Network Places versus Network Neighborhood (assuming your desktop is visible), but in essential look and feel, the similarities easily outweigh the differences.
To determine what’s running, you could open the Control Panel, open the System applet, and read the dialog box. But that’s a pain. Instead, you can use these techniques to remind yourself.