That was pretty much my predicament, only it was exactly three years ago and the two Windows were Win2k and XP. I installed Ubuntu Linux 5.10 and pretty much stopped finding reasons to keep the Windows installation around.
Now I'm happily using 8.04 and looking forward to my upgrade to 8.10 that came out today. My sixtyish mother will be staying at 8.04 as that is an LTS (Long Term Release) that has support for three years.
I just finished downlaoding the 64 bit version of 8.10...Will put it on my AMD Quad Phenom...and see if I like it..