Memory Compatibility?

Depends on your motherboard (especially the chipset it uses). A lot cheaper motherboards have lots of RAM compatability issues, so I would say the best method is guess and check. If you pop in this new memory, and your BIOS doesn't POST, you know what the problem is. Running with two types of RAM can also be problematic as far as system stability - IE, your computer will boot, but suddenly when you are running something that requires a bunch of ram, you will have unexplained crashes or BOS (blue screen of death). Keep that in mind. The ideal situation would be to have the same size and brand of RAM, the RAM being fully tested and certified for that chipset/motherboard. Of course this isn't always possible. You can do google searches on your mobo to find out issues with it and certain types of RAM. Be bold.

-IR

Many motherboards cannot run the RAM at the rated speed when 4 sticks are installed, so you may be able to get additional RAM to be recognized, but it will proably be running at a reduced speed (more wait states) so your performance may actually be worse.

Also try your new memory by itself (you will now have 2GB instead of just 1GB) to see if your computer is faster. Often 2GB is kind of a "most needed" condition - more RAM won't help much.

You can use profiling software like "CPUz" (free) and "Sandra" (free) to tell you what you have, how fast it is running, and suggestions for how to optimize your computer.

nicely in the beginning, PC2700 is an older form of ddr ram. in general in recent times it is common to apply ddr2 ram at above PC4200. however the considerable element you may desire to appreciate is what varieties your motherboard helps, different than that, there's no longer plenty to rigidity approximately. yet you may wanna improve. i haven't used that "sluggish" form of ram in a pair of years. ATM i've got have been given PC6400.

leave the chips in the slots they are in and install the new chips in the remaining slots they should work fine

They should be fine. They are rated the same type/speed as what you have....

if it was mine I would put the same part that's in it now but that's just my opinion.