With multiple apps open, just like you've done but, you need to hover the mouse over each thumbnail to enable the ture aero peek. A good example is to have several internet explorer tabs open and hover the mouse over each of them.
also it wont work if the app you are trying to get is either minimized (this one is a mixed bag sometimes it works sometimes it dosen't...) or maximized (also a mixed bag...)
and i also see you are using minefield so that can be it too..:sarc:
can you try it with another application?
My Computer
At a glance
Windows 7 Ult x64(x2), HomePrem x32(x4), Serv...Turion X2 ultra (oh well came with laptop)/P4...OCZ Dual Channel 4GB kit/ 1gb Dual ChannelHD 3200 graphics /GMA x3100 (yay for intergra...
Computer Manufacturer/Model Number
Tx2500z Tablet Pc/Homemade Server
OS
Windows 7 Ult x64(x2), HomePrem x32(x4), Server 08 (+VM), 08 R2 (VM) , SuSe 11.2 (VM), XP 32 (VM)
CPU
Turion X2 ultra (oh well came with laptop)/P4 @3.2 (yes P4)
Motherboard
IDK HP Motherboard / Intel DG965SS
Memory
OCZ Dual Channel 4GB kit/ 1gb Dual Channel
Graphics Card(s)
HD 3200 graphics /GMA x3100 (yay for intergrated!!)
Sound Card
Realtek HD Audio(mic working, well sort of)/Siig IC-70012