ID's misbehavior with Windows OS functions is a long-standing annoyance. I reported the “bottom of the window hides behind the taskbar” bit way back in CS3, from what I recall. ID starts in a restored (windowed) mode that is almost indistinguishable from full screen. It does this almost regardless of what its window size was adjusted to last time out. No idea when they're going to fix that behavior, or any of several other issues with Windows chrome (like the fact that a “New Folder” in a Save dialog is created without its name field open for editing, or that none of the Save or Open dialogs are scrollable with a mouse wheel until you click in the directory listing, sometimes more than once).
The one that annoys most, though, is ID's trick of “opening” as a tiny, super-minimized window partly outside of the top left corner of the screen.
Report the bug. The more who do, the more likely it is to be addressed in the next round (or even in a dot release).