Question : HP Desktop memory

I have a HP Elite 7100 desktop with 2 x 1Gb RAM in it running XP.

I'm about to upgrade it to windows 7 64 bit and bought another two 1Gb memory sticks.

I installed them and when i boot up the desktop it loads to the windows desktop and i can use it for 10 -20sec but them it just clicks off and automatically reloads.
I thought the new memory and the original weren't compatible so
I tried putting the new 2 x 1Gb in on it's own and exactly the same thing happens.

when i just have the original 2Gb in it works fine.

I've noticed the memory has a different part no...

The original is:- 1GB 1RX8 PC3-10600U-9-A0
The new is:-      1GB 1RX8 PC3-10600U-9-AP


Knowing nothing about memory is the AP so different to the A0 that it wouldn't be compatable with the HP Elite 7100 or is the memory defective.

Answer : HP Desktop memory

I did try the new RAM on their own and it failed, i'll try the original RAM in different slots.