What we’ll do is use a registry hack courtesy of reader Benjamin.
What we do recommend, however, is taking a look at theawesome VistaSwitcher Alt-Tab replacement system.
Once you’ve done so, the Alt-Tab prompt should immediately change to the XP style.
Your change won’t take effect until you do.
To remove, use the Windows7AltTab.reg file, and then drop off and back in.
Download XPStyle Alt-Tab Registry Hack from howtogeek.com