Problems with a new ram stick?

[croduh]

Hi all,

Decided to give my pc some make up and bought another 512 ram to it.It now has 1.3 GB.2x512 and 1x256 RAM, all same type,speed,model,company.
Since i installed it i have been getting some nasty lock ups, windows crashes and bsods while playing games.I assume the new stick is causing it, since it didn't happen before.
What could be the problem?I might try to re install it into the motherboard.Could it be that it's just plain broken or malfunctioned?

Rest of my machine:

Win XP sp2
amd xp 2200+(1800mhz)
gigabyte ga-7n400 motherboard
400W power
radeon 9200

[hyster]

are the 2 512 sticks in the same pair of slots? memory slots are in pairs so make sure u have them in slots 1-2 and the 256 in 3 or 4. dosent matter if its in 1-2 or 3-4 just as long as its the same pair

remove the new stick and use ur pc as normal.if still locking up remove/replace each module in turn.also try the module in the spare slot.

[croduh]

Thanks man, i'll do that later today.I have my 256 stick and 512 together.