crash crash crash

[cleansafe]

ok
when i first start a game i can play for almost 30 minutes before i get my crash. then i will restart the game and the crash will come sooner.
and everytime i restart the game the crash comes sooner ans sooner. unitl eventually it will crash whe the game starts to load the save file. i can wait 24 hours and do it again and the process starts all over again. im guessing that something is being filled up memory or something to that nature.
any suggestions for me to solve this.
i have tried everything on this forum. im running the latest patch and all drivers are up to date. on a side note everytime the game crashes i get a error report window stating something to do with civilization4.exe

my specs
p4 2.8ghz
1.5 gig of ram
ati radeon x850
24bit soundblaster

 

[Neon Deon]

What type of crash do you get?

CTD (crash to desk top)

Lockup(computer just freezes)

Reeboot(the computer just reboots itstelf while playing)

any error reports that came with these crashes?

 

[cleansafe]

crash to desktop
i get an error message to send to microsoft.
it pertains to civilization4.exe