Upgrading RAM, HP ZD8000 notebook

I am considering upgrading the RAM in my old, extremely sluggish HP notebook, but I'm not sure about what to get.

The computer is a ZD8000 (PW944EA#AK8).

I ran Crucial's memory test which was inconclusive (i.e. it "couldn't make a complete match" ); but it did tell me that I have a Quanta motherboard, model 3082, and DDR PC2-3200 RAM.

Currently, I have 2x 512 sticks, and they read "2 Rx16 PC2-3200S-333-12" (I opened and looked). I want to go to 2 GB (the maximum, if I understand things correctly).

Kingston's (manual) memory configurator does produce some results for "HP/Compaq Pavilion Notebook zd8000 Series (CTO)", linking to DDR2-400 or DDR2-533 modules from their range ("Kingston DDR2 PC3200/400MHz HP/Compaq 1GB (KTH-ZD8000/1G)" and "Kingston DDR2 PC4200/533MHz HP/Compaq 1GB (KTH-ZD8000A/1G)" respectively).

So, in other words, I have no idea what to get, and any help would be appreciated! There seems to be som incongruities between DDR/DDR2 and the MHz value (the bus speed?), etc....

I'm hoping that a RAM upgrade can stave up having to get an entire new system for a while longer (although, truth be told, I long for that day - I have decided to try to build my next computer myself, so that ought to be interesting...).