Oh, ok. I went to check my xp machine and I see what you mean. Don't worry about it. They are named differently (I see pf for xp and memory for 7) but they both show the combined (RAM + pagefile) space on the full bar gauge and the lit up bit is how much memory you are using.
No, don't turn off pagefile. I told you, you are very likely to run out of RAM and use pagefile.
If you turn your pagefile off, you will almost be certain run into system stability issue!!!
Get RAM upgrade, you will see faster performance. I really don't think you are safe to turn off pagefile until you get 8GB or more.
Even if you do turn off pagefile because you have enough RAM, there isn't much gain from doing so. IMO, the most honest article on whether you should turn on or off pagefile on a traditional mechanical HDD is this one:
http://lifehacker.com/5426041/understanding-the-windows-pagefile-and-why-you-shouldnt-disable-it
I personally don't turn it off even I have lots of RAM because some program will use it even if you have enough RAM. Finding which program use it and which don't is just too much effort for me and there isn't any real performance gain by doing that.
So, in conclusion to above, if you are running out or RAM, find out what type of RAM your mobo support and get some more RAM.
Ok, for the 100% cpu usage. Can you find out what process is hogging up the resource in process of task manager (show process from all users)?