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Have 2 sticks of 2GB Crucial ram in my PC and its worked faultlessly at performing operations for me. Its quick, speedy and much more noticeably quicker than the 800mhz ram in my laptop.
As it came with the PC I can't comment for ease of installation really but having installed ram before there all pretty similar, just flick out the catches and slot it in and thats about it, your computer should recognise it instantly.
On Windows Vista you will struggle if you only have 1GB Ram, you need about 2GB to make it run completely smoothly.
I personally have 4GB Ram in my home system and this is something that is a worthwhile upgrader so long as you buy the right type of ram, get a PC scan from www.crucial.com and it will tell you what type you need and also if you run a standard 32-bit operating system (most computers come with it as standard) you system will not recognise anything above 3.4GB.
This means you can install 4GB but it will only effectively see and use 3.4GB of it, this is the silly limitation for Im not sure what reason Microsoft put it on.
However be warned that if you opt for a 64-bit operating system, it will utilize all of your ram more or less whatever you put in. (I think Vista basic 64 bit has an 8GB cap) but you could put 128GB in and Vista Premium and the others would use it, the only downsides to a 64-bit operating system is compatibility. There are some things that won't work with 64-bit OS so just be careful and any Printers or peripherals you buy have 64-bit drivers for them.
Would be faster however I don't know how much faster if I were to use 1600Mhz ram, but you have to weigh up the costings of it all