Using the Control centre, just disable your side screens so you only have the one in the middle working. SAVE that as a PRESET.
If you're in eyefinity mode right now, open VECC and save the current eyefinity setup as a PRESET too before disabling as above.
Now, when you know you've got a game that only uses one screen activate that PRESET beforehand.
#1: Phenom II C2 955BE @ 3.6, Antec Kuhler 920, Gigabyte GA-MA790FX-DS5, Asus 5870/V2, ASUS Xonar D2X, 4 x 1gig OCZ2N1066SR2GK @800, Antec Truepower New 750, Arc Midi, Vistax64
#2: Athlon 64 X2 4200+, AGP 1950pro, Audigy 2, Asus A8V-D, 2gig ram, Enermax 465P, Antec900case. Now on Win8.1pro cat 10.2