Will this RAM work?

I have an EMachine T5212. It currently has two (2) 512 memory sticks in it.
According to the T5212 specs the type of memory needed for this machine is
1024MB DDR2 (2 × 512MB), 533MHz (PC4200) Expandable to 2GB.
I went to BB and asked for 2 1GB sticks that would work in my computer.
They gave me 2x1GB PNY PC2-5300 DDR@-667/533/400. Just checking before I open them - are they really compatible with the T5212? I only ask because theylook different than the ones that came with my computer--they have a silver cover over each piece of memory and the original ones don't.

Also, must I replace both 512s at the same time with the same size new memory?
Or can I replace only one and still have it work right?

Thanks for your help.

 

the silver cover sounds like a heat spreader and I would change both to give you 2 full gigs

 

Thanks. I'll do that after I get the malware off my computer (that MG is helping me with...boy, you are all livesavers wiht your patient and information!)