Tweak UI's “Prevent applications from stealing focus” doesn't work

[Angrist]

Here's a scenario: I am browing the net when I suddenly want to read my mail. So I click on my Thunderbird shortcut and click the Firefox window again and continue surfing. When Thunderbird is ready, it becomes the active window: it 'steals focus'.

Or I'm chatting while I'm installing a new program. Suddenly the install program pops up and asks me if I want to overwrite a file (or whatever). I happened to almost be typing a space. But now my space hit tells the program yes or no. I never even saw what it asked me.

Tweak UI is a program from MS and let's you, ehm, tweak your Windows UI. The only reason I got the program is to 'prevent applications from stealing focus', but it doesn't work.