Need help

[Bardolap]

And now for some ACTUAL help:

If you go to your options (Alt-O by default), there is a tab called 'Keys' that is to select hotkeys for various tasks (including toggling window displays (i.e. opening and closing various windows)). If you choose the UI category under the Keys tab, you'll see what I'm referring to. Most likely, you accidentally pressed the hotkey associated with the group window. I checked mine and it's set to ALT-P (By the way, it's actually called the "party window"
Try pressing ALT-P to see if it comes back on.

Also, you could use the EQ menu, choose players and choose "group status." This will toggle the window display as well.

Hope this helps!