Temporary use of Aero even when deactivated?

Hi folks, I have disabled Vista's Aero to speed up my system but
yesterday I accidentally hit a combination of keys when alt-tabbing
through my open windows and the Aero thing briefly kicked in where I
could see all my open windows in the 3d style stack. But now I can't
replicate that same combination and was wondering if it's a known
thing that someone can share because that was the one aspect of Aero
that I actually found useful.

In its absence till now I've been using a freeware app called
Freewheel that allows me to scroll back and forth through my open
windows using my mouse's scroll wheel. I'd uninstall it if I could
figure out how to turn on the Aero thing again.

Any suggestions?

Thanks in advance,
Jo