UPDATE: I just aborted the write, ejected the disc and popped it back in. The icon of the E: drive changed to like, a Windows Vista installation program-type icon, and loaded up the Windows Vista Installation menu, so I believe everything may have worked out.
However, to test it, I downloaded VirtualBox, and am using it to test the disc to see if it loads/installs Vista from the disc properly without issues.
I'm at the "Install Windows Vista" screen right now, in VirtualBox, so once I fully test the disc and see if it installs Vista without issues, I can then edit the disc in vLite, remove all the stuff I don't want Vista to install (Windows Live Calendar, all the preloaded HP stuff).
I guess it doesn't really matter if I abort the write process once it hangs at 99%. Seems I've wasted 2/10 of my DVD-R's because of the hanging issue (I previously made 2 copies in attempts to burn the ISO to the discs, and both discs had the hang issue)