A good tip is to make a new folder somewhere outside of "Program Files" and also not in "My Documents".
Name the folder "PS2 Memory Cards", and use it for your memory cards from now on.
This way, you can just point any existing (or new) revision of PCSX2 to that, and you'll be good to go.
It's also handy to do it this way, because if you ever uninstall PCSX2, it shouldn't delete that folder because it's not a part of the default installation folder structure. (I'm not use if this is so; this statement needs verification).
I do the same thing with the PS2 BIOS Files that I so painfully had to get from my PS2 Console;
ie: they exist in a separate folder called "PS2 BIOS" so i can just point any new or existing installs to it.
Anywho, I keep these 2 folders on a the same secondary Hard Drive that I have all of the PS2 Game ISOs I ripped myself, so if my OS Drive ever gets messed up, or if I buy a new PC, I won't loose any of my Saves or the BIOS, or the ISOs, and it's easier to transfer it to a New or Different PC.
I just gotta physically move the HDD to the other PC, then just install PCSX2 on that other PC's OS Drive.