To add to Tracy's answer, since you're seeing the pagefile.sys file grow over time, that indicates it is set to have a dynamic size, ie. grow as needed. Thing is, windows doesn't then shrink the file when that extra size isn't needed. If you set the virtual memory to have a fixed size (maximum and minimum size the same), or to have a specific maximum size (regardless of what the minimum is set to), it will not grow beyond that.
Look up the specs for your particular motherboard and see what the maximum amount of RAM is that it is physically capable of utilizing, and then buy enough memory to max it out. That'll help your performance some.