|"Iam just saying it depends on motherboard"|
I agree. I have a Shuttle board that will run 3 sticks in dual channel mode provided it's setup right. But these are exceptions, not the general rule.
"I boot up my pc and it show that the ram are
not put equally"
Of course they're not equal. 2GB doesn't = 512MB. You can try switching the sticks around in the slots to see if you can get dual channel mode to kick in, but I doubt it will happen. Intel boards are not the best to work with.
"my total memory is 2.5gb and available memory is just about 2gb"
Where are you getting that info from?