HP Pavilion 23xw Dual Monitor Issue

I currently have the Late 2012 Mac Mini, 2.5 GHz i5 connected to one HP Pavilion 25xi monitor. I bought a newer HP Pavilion 23xw to use as a second monitor but, obviously, it's not working for its intended purpose. The ports on the back of this monitor include 2 HDMI and a VGA (which I'm trying to use). The HDMI connection works fine, as I tried using my Xbox 360 and it worked just as it should. However, the problem: when I try to connect my Mini DisplayPort to VGA Adapter (official Apple brand) to the computer and then to the monitor, the computer completely locks up (but doesn't shut down). The screen goes very dim on the 25xi monitor, and the mouse and keyboard become unresponsive. On the new 23xw monitor, there is a very strange pixel anomaly in which there are several vertical lines that repeat on a loop. This is when the VGA is active, by the way.

I have some ideas of how I could try to fix this, but I wanted some input (and hopefully a single solution) so I don't have to spend tons of extra cash.

1.) Upgrading to 8GB RAM. I read around and apparently a dual monitor setup doesn't require too much more, but maybe I have some kind of isolated case.

2.) Changing from a VGA Adapter to HDMI Adapter. This is the one that I'm probably going to go with, unless somebody has a better idea. I'm thinking that there is something wrong with the current adapter or cable that's locking up the system.

One more thing: my friend suggested that I try connecting the monitor to a separate outlet, in case there is something wrong with the sharing of amps or something. I tried that today, and it didn't work. Just in case somebody was going to say that.

Hopefully I provided enough information so that you can help me! I have been messing around with this for more than a month now and it's time to solve it. Thank you in advance!