after some hours trying i was able to install MacOsX 10.5.1 (Kalyway) at my Alienware Area-51 M5550 (1.6GHz Core2Duo, 1GB DDR2-667, ATI X1400 and Intel 945PM + ICH7 Chipset)
but when i boot up it appears that white screen with the apple logo in gray, after like a minute the screen goes black then black and white stripes and then goes black again and nothing else happens
could it be the videocard driver? i installed the ATI x1xxx drivers within de kalyway dvd

no its not the video card im some what running it on my alienware m5550 and i have the same video card as you, problem im have with mac my self is the wifi and sound dont work and the screen resolution is rele bad so if u have goten past these problems like me know