[Gravter]

If your not sure what RAm you have and you have never opened/upgraded anything in your pc, then go here:

http://support.dell.com/support/topics/glo...=gen&~ck=anavml

Input your Service Tag (serial number) and it will show you exactly what it came with.
It'll tell you if you have one stick or two, etc...
Of course like someone already mentionned, you could install and run "cpu-z" (http://www.cpuid.com/) and it will show you the same info.
Those 4600 are fairly easy to open up and change the memory in no time.