This forum is called "Say Hello" so let me do that first: Hello!
I installed Ubuntu 12.04 into VirtualBox 4.1.18 with Win7 64 bit (4gb ram, dual core) as the host OS. 12.04 was running pretty slow (I had a geek friend make sure my VBox settings were all optimized). But 12.04 was still running too sluggish. He suggested installing xfce which I did. Now it's faster and more responsive. Yay! I was going to ditch using 12.04 in VBox but now (with xfce) it's working fine and I'm a happy camper. Apparently the Unity interface is a bit of a resource hog.
This forum has already helped me fix one issue.
Acer Aspire 5732Z, Dual Core, 4gb ram, Ubuntu 12.04 with xfce running as guest OS in VirtualBox. Host OS is Win7 64 bit.