Something isn't right.
VPC would only use memory when it's running. Once in a while a program will terminate and not release the memory it was using. I'm not sure if this is the case in OS X but it used to happen a lot (and double especially in Windows). But restarting the computer would fix that problem. In sum, if VPC isn't running, isn't installed on your system, and you've restarted your computer, then VPC isn't using any memory.
How are you arriving at the conclusion you are missing 224MB? Is that what you get in the "about this Mac" window? I'm not sure why that would be. Even if you have VPC running and have memory allocated to it, your Mac still knows how much RAM it has. With or without VPC running my computer still reports the correct amount of RAM in the system.
It's possible that some of your RAM has a pysical problem and disappeared from the system. It can die, break, fart, go AWOL, etc but that's not common. What's even stranger is that it's 224MB. If you were missing 32, 64, 128, 256, etc it would make more sense because that could be 1 stick of memory going out. 224 would take a big combination of sticks going out (1 128 and 3 32MB for instance) and most people just don't have their computers configured that way.
So basically this still doesn't make sense. Let's get very detailed. What kind of system do you have, and what OS? 608MB is a strange amount--how is that configured? 512+64+32? Is there anything else interesting/special about your computer (dropped from high altitude, blessed by a priest, etc)?
You could pull your RAM out and put them back just to be sure they're seated--but what would unseat them in the first place? Just for laughs you could zap the PRAM (command+option+P+R while booting, let it gong 3-4 times) but that's a longshot.
