Sorted!
I added the following line to XF86Config so that it looked like this:
Code:
Section "Monitor"
#    ModeLine  "640x480"   25.175  640 664 760 800
#                                  480 491 493 525

# 800x600 @ 56 Hz, 35.15 kHz hsync
#    ModeLine "800x600"     36     800  824  896 1024
#                                  600  601  603  625

     ModeLine "1024x768"    46.0   1024 1032 1176 1344
                                    768 771   777 806
EndSection
Thanks for trying to helpHTRegz, appreciated!