Laptop RAM matching question

I currently have the following two slightly different SDRAM sticks in my laptop: a Hynix 512MB DDR2-667 (PC2-5300S), and an OCZ 2GB DDR2-800 (PC2-6400). More memory device details at the end. I just put in the 2GB stick today (it replaced a second 512MB Hynix), and so far everything works fine, but I wanted to double check over here if:

1. Is it okay to use the OCZ's DDR2-800 SDRAM in my laptop, given that the only supported memory types are DDR2-533 and DDR2-667 SDRAM, and according to an HP Chat support professional "You notebook support only DDR2 667 MHz memory. So the above mentioned 'DDR2 800 ' is not compatible."

2. Should I replace the 512MB Hynix stick with another matching 2GB OCZ stick (which I already have courtesy of OCZ's warranty replacement service), even though my laptop can only use up to ~3GB of RAM on the current 32-bit WinXP platform (It can use all 4GB if I switch to 64-bit version of XP or to Vista.)

3. How can I tell how fast the OCZ ram is running? (I ask because the OCZ support tech told me "it probably runs at 667MHZ not 800MHZ" when I asked him or her (2 letter Asian name?) about the incompatibility (not supported) issue with DDR2-800 memory type).

Below is some possibly relevant info per Everest software. Please let me know if you need more (I cut out most of the Everest reports):

Thanks.