I finally did it! After installing all of my essential apps in Win 7, I knocked off the fear of installing Ubuntu 9.04 inside it. And guess what? It works! The same! Identical!!
So here's what I've learned:
Ubuntu 9.04 CAN be installed safely inside Windows Vista (x86) and Windows 7 (x86), and that my "replacing root.disk" trick works! After i installed a 4GB chunk of Ubuntu inside Win7, I ran Ubuntu, then back to Win7, and replaced root.disk. And fortunately, it works!!
One thing that I have to bring up though, is that when I try to boot into Ubuntu (it's installed inside Win7 now), this message appears before get to the Ubuntu boot screen:
Try (hd0, 0): NTFS5: No wubildr
It brings me to that screen and lasts there for like 40 seconds. I have no idea what that means, nor do i care about the 40 second delay, but all i know is that Ubuntu is working perfectly. I have successfully migrated from WinVista to Win7 with Ubuntu tagged along! *applause*