For reasons which don't hold much weight if I am willing to spend more time figuring it out myself (such as need to use Sopcast for watching soccer online), I have always had a dual-boot system, even in the ugly days when I was a RedHat/Fedora user. And my ext3 partition which hold Ubuntu 7.04, is just a small 10GB OS-only partition and my data is still on a NTFS partition that is accessible by both Windows XP and Ubuntu.
So, I have never needed to access anything from my Linux partition from XP. But, seems like there are enough free tools available to achieve this. The most useful being Linux Reader (freeware and closed source) and Ext2 FS (freeware and closed source). The options are nicely analyzed and explained here.
(p.s. Interestingly, I wasn't the first to think that I could prefix 'ubuntu' with my name/initial and it would be a clever blog title.)