Computer wont start with 3 ram modules

[Raid1992]

i cant install 3 ram modules
1GB DDR2 555MHZ
1GB DDR2 444MHZ
1GB DDR2 800MHZ

Blue screen Appeared

 

[battlefieldhazard]

if its dual channel then you have to use 2 sticks at a time and they all have a difrfrent speed so you cant do that it would be contradictory

 

[Raid1992]

thanks

 

[Raid1992]

but it worked before i install another 800mhz 1gb ram