You should remove those music last.fm sticks from your computer might have issues!
jk
The best way to ensure compatible memory is first update your BIOS as they normally add newer compatibility to RAM and get the latest motherboard manual which will have a list of RAM it supports.
Ensure it's on the list.
Check the DDR version matchs, well this is simple enough it will normally be DDR2, unless you have a newer computer or a really old one. DDR2 comes as DDR2 PC 2700 to PC 8000. Ensure what speed your motherboard can support or has previously in there.
Check the timing/speed of the memory against the old stuff. If it's slower, remember the motherboard will set it to the slowest one, which can be a waste of the others performance.
Check the pins match, 240-Pin or whatever. Check if non-ECC or ECC, some motherboards don't support it.
Double sided RAM, or single sided RAM, makes no difference. Heat sinks cost more but at good for overclocking and staying cool and stable.
The voltage off by 0.01 won't matter.
When installing them check if your motherboard is single, duel or tri channel. Normally it's duel, this means you install the first lot in slots 1 and 3, second in 2 and 4, for the best performance (lots of 2). Newer computers will be tri, which means lots of three RAM is best performance.