HP Pavilion DM1-4108AU Notebook computer came with 2 Gbytes of RAM. An extra 4GB of Single DDR3 1333 SODIMM RAM (Kingston KVR1333D3S9) cost only $23 from MSY Technology Pty Ltd. The hard part was getting the back off the computer, in order to put the RAM in. Rather than a small panel held on with a screw (as with my old Kogan Agora), the whole back of the HP comes off in one piece. This makes it easy to access the fan and disk drive as well as RAM, once you work out how to get the back off. To do this you first remove the battery and then, keeping the battery latch slid fully open, slide the whole back of the computer off. This is very difficult to do the first time (with the fear of breaking something).
I bought my RAM at MSY's Sydney Ultimo store (behind Sydney TAFE and University of Technology Sydney). The location of the store is hard to find as it is on the end of a block overlooking a park (not on a road). Going into a small nondescript door, I found a bustling computer store with a queue of people getting rapid but knowledgeable service from the staff.
With the memory purchased and the back off the computer it was easy to upgrade the RAM.