CIV4 crashing xp pro sp2

[aim2pls]

Hi all,

civ4 is crashing my xp pro system
1) reduced graphics to low >> crashes less often

system
ati 8500dv w/64mb
intel motherboard with P4 2.4 processor
1 GB main memory
4 GB static virtual memory (on secondary drive)

If anyone has any ideas ...plese help